AIBU to think my friend keeps undermining my marriage?

You are not being too sensitive. This would piss me off mightily too. Id either stop seeing her, share way less information with her or challenge her every time till she packs in (maybe resulting in her choosing not to see me). Depending on how much I liked her. As many have said, she is almost certainly unhappy but that doesn’t help you.
Challenging would consist of going back to basics to point out her unreasonableness in a slightly puzzled tone. (Keep the questions going till she admits she is wrong or changes the subject)
I find that really weird, it would be nicer if he bought you gold
Why would it be nice for him to buy me something I don’t want rather than something I do?
I can’t believe he would leave you when you’re pregnant.
Why would you expect him to go against my wishes? I’d be really cross if he ignored my opinion because he thought I knew best. Do you prefer your husband not to take your wishes into account? Why?
my husband would never do that
Never take your opinion into account? Why is that ok with you?
well they know my husband is my best friend and I tell him everything so they wouldn’t dare
So why are you worried then?
I know your husband is less protective
He trusts my judgement. Does your husband stop you from doing things? Do you need help?
maybe your husband isn’t as dominant
What so you mean by dominant? Does hyour husband dominate you against your will? Do you need help?
she wouldn’t have that issue. because her husband is amazing and she only has issues with her family.
So why do you think my suggestion is not applicable for your family?
You get the idea - you could have fun with it to see how long it takes and it will stop it riling you up.

So why hang around with her, then?

I agree that plenty of people are like this, but those people don’t become my friends as they are weird and annoying. If my friends were to suddenly start being like this, I would see them much less and they probably wouldn’t be my friends any more!

I read half that...
She's a vampire sucking the joy out of your life.
You need to make much less time for her in your life.
When friends turn toxic 😆

She's not your friend. You know that, surely.

Please stop telling her personal details about your husband and marriage, it's very unfair to him, as she sounds quite vindictive and is definitely gossiping about you both, I'm sure he'd rather she did not have so much ammunition to slag him off.

Bloody hell she sounds tedious and not too bright!

Are you really getting anything from this friendship? It's fine to drop people who make you feel shit.

She’s being bloody rude and obnoxious, YANBU or over sensitive at all to dislike it.

I find as I get older I am really losing the appetite to put up with ‘friends’ like this, but I have done way too much putting up in the past. I’d either pull her up on it really flatly and assertively each time she does it, ‘stop making critical comments about my husband, it’s rude’. End of discussion, you don’t have to justify yourself. If I had to repeat that more than three times then honestly I’d sack her off.

If you’re generally fond of her, you could just try repeating ‘nice for you, not for me’ as a PP recommended, and hope she gets bored.

Or, you could just start spending more time with other friends who aren’t like this. But I think I’d want to explain to her at least once what the problem is, as although it’s wildly annoying I suppose it’s always possible she doesn’t realise that she’s doing it or how wildly annoying you find it. I feel like if someone was once a good friend you should probably give them at least one clear steer about what they’re doing that you don’t like, and give them a chance to change it, before you distance yourself.

She sounds like she is absolutely miserable in her own marriage and quite frankly not allowed an opinion against her DH (Not allowed out late, the comment about her and him being best friends and sharing everything, how he's the serious one, how her husband is amazing and they'd never have anger issues).... It all points to her own insecurities.

I'd probably get pissed off and snipe back at her TBH and say things like "I'm pregnant, I'm not an invalid, I'm actually looking forward to the break".... or "I don't like gold and my DH knows that about me because he's my best friend" 😂

This person is not happy in their marriage op. Sadly it would appear ‘subtle’ digs at others (ie you in this case) make her feel better about herself and her marriage. If you can take it in that context, and can be bothered, then answers such as Wherethefishes suggests are a great idea. Or recognise life is too short and distance yourself from an increasingly toxic person. I’d do the latter myself..

Sounds to me like she's trying to make a virtue out of some of her husband's less appealing traits.

She's not a friend @suziequeue1 at best she's a frienemy

It wouldn't feel disrespectful because her comments have absolutely nothing to do with your relationship. Tedious, yes.
My gut reaction would be to deflect it right back to her. I.e. "you husband is jokey and I think husbands should be serious like mine" well, good job you are not married to my husband then, innit?
But the next thought I have would be, if I have to work so hard to keep this person in line, do I actually want to hang out with them?

Sounds like she's still in the "honeymoon" phase trying to work things out re marriage - thinks she knows it all because she's not long just tied the knot. Also sounds very insecure. Very annoying indeed - as others have said, maybe set a clear boundary with her when she makes these comments.

I once read that (paraphrasing) ‘once you realise most negative things people say are just projection, you stop taking anything personally.’

If it was me I’d decide if I liked her enough to put up with it and if ‘yes’ then find a way to ‘yellow rock’ it and focus the conversation on other things. I do have a friend who’s a bit prone to comparisons, but I love her other qualities so I just smile and shrug through the irritating bits.

But it doesn’t matter what anyone else would feel. You don’t like it! What do you do when she makes those comments?

Oh it sounds tiresome! Why not just stop spending time with her? Get a taxi (or bus?) to your appointment.

Sounds like she's not happy in her marriage.

If she was perfectly happy in an amazing equal marriage she wouldn’t try to make herself feel better by putting you down. This combined with an always right type personality is probably very wearing. If I were you I would try and withdraw from the friendship, as when you have your baby (especially if she wants a baby), this will become unbearable and you won’t have time or energy for it.

OP, I’d be asking myself why you appear to be friends with someone you feel is continually criticising you, and why you’re so insecure that you feel someone else’s comments are ‘undermining your marriage’?

Without doubt this will be because all is not right in her marriage, which is sad, but doesn't stop it being irritating for you. Try not to take it personally, I expect she's constantly trying to defend his behaviour to herself. You can either distance yourself from her, or just respond calmly and positively with statements like, "it's a good job he's married to me then isn't it because I think his decision/behaviour/way he acted is perfect/lovely/kind". Or, "oh do you think so, no I disagree." Then just move on and discuss something else. Sounds like underneath, she's actually going to need good friends around her.

Well it screams that she’s insecure in her marriage. But be nonchalantly defensive back:

”Well I’m just glad my husband knows me well enough to buy the bag I want instead of the gold I don’t”
”Isn’t it weird that your husband wouldn’t do his best to provide for his family when they need it most! I’m glad mine does.”
”I’ve found in laws aren’t always that perceptive to realise we tell each other everything!”
“Oh there’s a fine line between protective and controlling, my husband will tell me if he’s concerned but totally accepts I’m my own person and I can make my own decisions about how late I’m out!”
”Are you okay with your DH being so dominating, I don’t think I could cope without my independence”

I suspect it’ll be a bit exhausting at first, but hopefully she’ll realise her way isn’t the only way, or get bored of hearing how great your DH is and shut up.

I’d let her crack on, comparison is the thief of joy. If she’s constantly comparing and analysing I’d say she’s trying to justify that “her relationship isn’t that bad” by any means necessary (even if irrational to everybody else).
I’d just say “fair enough” to everything she said or I’d withdraw from the friendship.