Blindsided at breakfast!

If F was shook by the whole thing she should have spoken up and defended you to N but she didn’t. At least not to where N could see her sticking up for you.

Why are you sitting around gossiping about other people? Incredibly tacky and inappropriate.

OP, you still haven't told us who was lying?

You say you interrupted and then persevered and F says you didn't.

Which one is true?

Yes this, is F a people pleaser who will take the side of whoever asks?

Also, you’ve given a lot of irrelevant info in your OP, it’s long winded, do you witter a lot?

In terms of N it sounds like you’ll never be best buddies, but that’s fine. Just remain civil on the occasions you see her.

I think you should proceed in the knowledge that N is a person you don't much care for, and who may behave in a way that offends you, and plan how to deal with that.
You have two main approaches I think. First, to be polite but detached and let her wash over you. Second, to fight fire with fire and give her back as good as you get.
What I'd strongly advise you against doing is getting it out of proportion and letting one person become the defining part of the group for you. You have four other friendships there and any drama arising from this is going to effect them all.
This includes resisting the temptation to talk about N to the others. Once this starts, the group's ruined because everyone is talking behind each others backs then one tells another and on it goes until there's no trust.

My advice....google Mel Robbins
#letthem

A great pity F didn’t speak up at the time! She took the easy route and messaged you later siding with you. She strikes me as wanting a bob each way, ie keeping in with both of you. Hells bells this sounds like playground stuff.

Going forward I’d give N space, don’t let her drive you out. Whether or not you were rude, I wasn’t there so won’t comment. But it does sound as if N is more outspoken than F and yourself. And quite frankly that can get on yr wick, one person holding the floor.

Sometimes people just don't get on. Maybe N finds you really annoying, just like you dislike her as well. You clearly don't see eye to eye or just have clashing personalities and that's fine and normal.
You got on her tits, she offended you, perhaps time to just call it a day as "friends" and just be people who go to the same group and who are polite to each other when necessary.

Good grief, people, never interrupting is for children and structured debates. Normal adult conversation consists of 'overlays' which are, basically, participants interrupting in a relevant way - which is what OP did.

I understand where you're coming from, OP, and well done on the self-confidence work! Your feelings about N's reprimand seem a bit intense, though. Try to channel that Frozen song. I'd give her more chances - and keep 'interrupting' when you've got something to add - to see if she calms down a bit She may just have been having a rough day.

We weren't there and to be honest op it is tricky to give much of an opinion on the conversation without more detail as to the content/how relevant your interjection was etc.

F has probably said similar to N tbh. ‘Newname was rude interrupting, thanks for pulling her up on it’ etc.

Life’s too short to go to breakfast with women who gossip about other people’s marriages and are shitty to each other. I honestly couldn’t think of a worse way to spend my time. Find new friends and/or a new hobby. Don’t waste time wondering how to navigate this, just ditch the lot of them.

"'can you stop being so defensive and let her finish"

That's an absolutely fair enough question.

There was no 'shouting' as PPs have suggested either.

Feeling passionate about other people's marriages being on the rocks, doesn't give you a licence to talk over someone and then persevere with it.

Even marriage experts wouldn't do that.

Reading the OP it sounds to me like N, certainly, and possibly also F, are in the habit of talking over the OP and, basically, ignoring her input. She says:

I find in this dynamic when the 3 of us are together (our children do the same hobby), they talk the most and I feel my voice is often unheard (have felt like this my entire life so I'm fully aware that that is my 'stuff'). They will unintentionally (I assume) talk over me or not always really respond to things I say.

On this occasion she made the effort to have her say and be heard and, it seems to me, N was responding badly to this simply because she is used to overriding and ignoring OP and couldn't accept her standing her ground and having her say.

You might think OP's reaction is OTT, but if it is a huge effort for her usually to stand her own ground then I can understand her being unsettled by the aggressive response.

I suspect N has interrupted people inlifetime. Just let it go but keep in mind you are not as close to N and let that guide your interaction with her. IMO it is possible she felt more comfortable responding that way towards you whereas with F(or someone else) she may have said something more neutral…or even admiring your passion or quick defense or some other interpretation of your interruption.

if you like F and feel you two have squared it I would go along without saying anything else. Politely kindly greet N but keep it at arms length.

I love a good gossip. It’s a fault of mine. This whole conversation feels a bit gossipy and I don’t think N had any high road here to interrupt you when she/F were talking about someone’s marriage

Perhaps you should all stop discussing other people's marriages.

F didn't feel interrupted. There are points in conversations where you can sometimes interject. No one has completely linear conversations where no one ever interrupts, that's unrealistic. As long as you respect each other and give each other a chance to talk, it's ok to interject at relevant points.

If you don’t like the dynamic with just the 3 of you, don’t go out to breakfast just the 3 of you?

Sounds like N was looking for a chance to shout at you.

You need to develop a tougher skin and answer her back every time. Well done for standing your ground.

And speak louder, don't let her talk over you ever again.

I did interrupt her/try to interject my opinion (I suppose unlike most of the time, I persevered in giving my opinion this time) when N, in my opinion, quite angrily and aggressively, physically turned towards me and said 'can you stop being so defensive and let her finish'. I was absolutely gobsmacked and felt like I'd been punched in the gut. I responded that I wasn't being defensive which she double downed on and said I was. I repeated that I wasn't and continued making my point.

Interrupting people is rude, when someone points out you’ve interrupted when someone is speaking and yet you continue to ‘make your point’ by carrying on interrupting them it’s doubly rude.

Take a look at the way you interact with people, sorry but you were in the wrong here.

Please. You were being rude. You admitted interrupting and talking over your friend. You got called out on it and you were ,left "shaking, sick, feeling like a punch in the gut". Massive overreaction! Huge drama over nothing.

Just be polite and say hello and then keep your distance. You don't like her anyway so just don't spend time with her unless you have to.

I did interrupt her/try to interject my opinion (I suppose unlike most of the time, I persevered in giving my opinion this time)

And I did apologise to F if I was interrupting her. She insisted that I wasn't.

So which one of you is lying? 😳