Made MIL cry?!

I'd write her a little note to say that you know that she will always always be his mother and that that doesn't need to be defended. Tell her that you feel like you've been entered in to a competition with her, which is not what either of you want surely.

That acknowledges both positions but doesn't ''challenge'' excessively. It's not an apology (as I agree, don't think that an apology will resolve things anyway).

Yabu

Say if you have a dad and he has always liked doing something for you, like checking your tires on your car, and it's your tradition when you see him. And your dp told your dad you should do that yourself you're a grown up and then when he said I do it because I love her, dp make a sarcastic comment about what else he does for you and your dad was hurt. Would you want to build a life with sometime who can be so vile?

^^ This

She does sound a bit overbearing but you sound really spiteful.

She's a PITA but you were unnecessarily cruel. Why basically state that you plan to force a wedge between them?
It's ridiculous that your DH sees her daily and also gets a packed lunch... but why are you even discussing that with her, rather than with him?

She sounds like she has a small life and a small mind. If she has done little else but raise children this stuff like sandwich making assumes a ridiculous importance that a more mature person (and I don't mean age) would not engage in. These are silly games by a silly woman, who has finally had it served back to her.

You may well be messing up her meal plan. Why not check first? I hate throwing spoiled food away, particularly if I've taken stuff out the freezer the day before.

Also, are you sending food you know she likes?

What would you do if it was reversed?

Say if you have a dad and he has always liked doing something for you, like checking your tires on your car, and it's your tradition when you see him. And your dp told your dad you should do that yourself you're a grown up and then when he said I do it because I love her, dp make a sarcastic comment about what else he does for you and your dad was hurt. Would you want to build a life with sometime who can be so vile?

As I said earlier, perhaps you don't have parents who are as nurturing as your almost in laws are to your dp and there is some underlying jealousy here?

I don't think what you said was awful. I quite like it, snappy comeback. But as you see, this has been turned into a hand-wringing performance in which you are the villain. She'll be enjoying that. If you treated her comments with indifference she'd hate that much more.

I think you both sound a bit silly, wrangling over your partner/her son like he's a juicy bone.

Don't engage with such silly nonsense.

I am going to guess however that she has relatively little in her life other than her children.

yes, that’s what I was thinking.

Bloody hell you expect her to apologise but don't think you've done anything wrong?

"I said he is a 43 year old man I'm sure he can organise his own lunch"
This is how it started - why did you feel the need to address this with her? If you have an issue with the situation, talk to him. I would get the ick with a man who allows himself to be babied by his mother, but it is him you should talk to.

"she said "yes but me I love my son" (emphasising with her voice that it must be in contrast to me)"
She understandably got defensive, so went on the attack

"I began to lose my temper a little so I said "do you warm some milk for him too?"
You escalated it further instead of de-escalating and walking away. Why did her comment get to you - why is this such a raw nerve for you? Do you doubt how much DH loves you? Do you see her as a rival for his time and affection?

"and she said "listen it's simple, I am the first woman of his life"
She escalates yet further in response to your attack. She is also showing her rather warped attitude to him: over-possessive and unable to let go.

and I said "true but I will be the last".
Witty, but also too mean.

Then she started crying and ran out of the room.
Unsurprising given how the argument ended.

Advice: don't get into petty squabbles with MIL as it just makes you look bad when she gets upset.

Separately, look deeply at what exactly you don't like about his relationship with his mother. Is it that you don't like him behaving like a child around her? Are you fed up with the amount of his time she takes up if she is going round there every day? Or are you irrationally jealous that he spends time with another woman? Would you feel differently if it was his father that he was spending so much time with?
Talk to him about it, not her.

Apologies are pointless imo. What both parties want is to be understood and acknowledged.

You need to do is understand that she feels she is in competition with you. She should understand that she's entering both of you in to a competition you don't want to enter. It's weird, for both of you surely.

I just told him now that this is his problem to find a solution for because it's not a problem for me

You do realise that the solution he's likely to choose is leaving you...

What a cold and nasty thing to say. I would have thought you meant she'll be dead before you too.
You started the fight by trying to belittle her because she enjoys doing things for her son.
You should apologise.

I'd be ripping the piss about the mummy's boy I was with instead tbh - to him, not her. Anytime he asked me to do something I didn't want to, oh your mummy will do it for you etc

butyou escalated things with MIL. How did you think it was going to end? One of you were probably going to end up crying if you both kept upping the ante.

Personally, I left that shit in the playground. She's not going to change because you came for her. She'll probably get worse so she can get upset again and make you out to be the bad guy.

And BTW, mummy's boys never change either. If you keep upsetting his mother instead of other approaches, you'll force him to choose between you. And he WILL choose her.

I do this too! My lovely DiL is so appreciative, I've started prioritising her favourite foods over DSs. Who will tbf eat anything.

Not sure why people are saying he is immature for accepting the occasional packed lunch from his mum. Maybe he's just a really nice person who can see it gives his mum pleasure to do things for him and this is a small way she can show how much he cares. And he can help her still feel useful.

They both benefit from this happening. Should he tell his dm to stop just because op thinks he's being babied? Or should he stick up for himself and his dm?

Yes. Just because you have a feeling doesn't mean the person was trying to make you feel that way.

It sounds very frustrating. Not surprised you lost your cool tbh

But you have different relationships with him. She wants to make him sandwiches, ok.
Presumably you have a real relationship with him. Do you communicate with him? Is he worth it?

I agree with this. I don't think it's normal for a grown man to see his mummy every day and get a packed lunch. I think you were quite restrained!

Hate to say it OP, but if your relationship comes down to a choice, you or her, he's going to choose her.

You can see that a mile off.