I had something like this happen to me years ago
I got on really well with my brothers then girlfriend
We where so close,she was the sister I never had and a fab aunt to my dc
Annnddd then she finally got married to my brother
She ignored me the whole time at her wedding (fair enough,your wedding day is all about the bride) and I went to the loo
Sat there,peeing away when I heard her come in with another friend
They started slagging me off-my hair,my make up,my outfit (that she insisted I buy and pay for myself),my weight,the fact I never married,the fact my kids are 'bastards' and 'horrid little brats' (they where not-they had their moments as all kids do),the money I was 'raking in' in tax credits,why should she 'single handed pay my rent' but the next sentence was 'she should have paid for my underwear,ring,shoes and paid more money into the bar bill',the fact I asked her once to have the kids while I ran to the shop for milk-that turned into 'she's always getting me to babysit',my looks and finally the fact I'm 'a slag who will shag owt'
I very calmly waited until they'd gone,walked out of the loos,went over to where their shitty wedding cake was,picked it up,walked out,hailed a cab and went home
Kids loved the cake for breakfast the next morning and I've never spoken to her since
I then went upwards and onwards-i re-trained at college,got a better job,kids grew up to be amazing adults,i have an amazing dp and we own our own house
She's had her baby (my nephew),found that motherhood isn't the rainbows and glitter she thought it was,the penny dropped that my brother is a lazy cunt who gave up his job the second he got her pregnant so he could stay at home,ignoring the kid and she has to work full time and rely on uc for top ups (which isn't the millions she thought it was)