Have name changed, as the details might out me.
A bit long, sorry.
My friend is upset with me, and has told my DP that she wants an apology. DP thinks I should apologise, but I don't want to as I don't think I've done anything wrong.
Background: My friend, though lovely, can be a bit thin-skinned and high maintenance. She takes offence quite easily and has a tendency to create drama where there really isn't any need for it. She also has very fixed ideas about how social/family things should and should not be done, even when these supposed social conventions are unknown to the rest of us!
This issue all started with her twin brother's upcoming wedding. Her DB and his future DW have been together a long time. My friend has never really liked the bride, and has never made an effort to cultivate a friendship or anything like that. Fair enough, there's no rule to say you have to be friends with a relative's DP! My friend's DSis is fairly chummy with the bride, on the other hand. The bride has now asked the DSis (along with her own DSis and best friend) to be bridesmaid. My friend was livid when she found this out a few days ago.
She reckons she should be bridesmaid because she's his twin, and is upset because she won't be a part of the wedding party, and (apparently??) that means she won't be in any of the photos. I thought she was BU, and told her so, pointing out that her DSis is much closer to the bride, it's the bride's choice, and that it's the bride and groom's day, blah blah blah. I was fairly diplomatic, I think. She calmed down a bit during our conversation, and while she was still pissed off about not being bridesmaid, I thought that was the end of it.
Yesterday afternoon, she sent me a text asking if I could talk. I told her I was a bit busy with a work-related deadline but said she could ring if it was important, if not I could speak to her that evening. She phoned me immediately. Turns out she was still furious about not being bridesmaid, and after she spoke to me a few days ago she went and booked a two-week holiday starting the day before the wedding!! Unsurprisingly, her DB is upset that his twin sister won't be there. Her DD is upset that she is going to miss her uncle's wedding. Even her DM, who normally placates her no matter what, is upset.
I told her I thought she was bang out of order. She disagreed. The conversation ended up getting quite heated. She said she couldn't understand why her DB was upset she wouldn't be there "as it's not like I'm even going to be a part of the wedding". She said her DM should back her up over the bride, and said her DSis had "betrayed" her by agreeing to be bridesmaid without asking if she was going to be one first. Her family have asked her to change the dates of the holiday. She does not want to because she will lose her deposit.
I tried to be diplomatic at first, but the conversation went around in circles and I ended up losing it with her (partly because I thought she was being an arsehole, and also because I was a bit stressed with work). I told her I thought she had no reason to be upset at not being bridesmaid in the first place, and that she had obviously only booked the holiday in a tantrum because she wouldn't be a key part of the wedding. I told her I thought she was being childish, spiteful and attention-seeking, and that she was being unfair stressing her mum out (her DM is getting on a bit, and has been in very poor health recently). I also told her I had better shit to be doing than listening to her whinge about not being the bridesmaid of someone she doesn't like and has made no effort with. She ended up hanging up on me (she has form for that).
She met DP in town today at lunchtime, and told him she was very upset and had been crying all evening because of how I had spoken to her. She told him to tell me she expects an apology or she will consider our friendship over.
WIBU? DP reckons I should apologise to keep the peace, and because it might makes things awkward with mutual friends. I don't think I have anything to apologise for. Maybe I should have been a bit calmer saying it, but I still agree with what I said. I also reckon it'll blow over, as she has told other people that their friendships are over in the past only to be best pals again a fortnight later 
So, Mumsnetters? Should I apologise?