I'll try and be brief 😬
BIL (DH brother) is a bit of a free spirit type, works as a DJ, spends a lot of time on the road, parties hard, you get the picture. A few years ago he met SIL (not actually married but calling her that for ease!) and very rapidly had DN1 (now 7) and DN2 (now 5). SIL was also the party type but obviously had to settle down when pregnant and having small children which BIL didn't really do, he carried on pretty much as before, hence them splitting up by the time DN2 was about 18m old.
When they first met SIL was quite dismissive of me, clearly thinking I was very boring as a mum of 3 young kids and never going anywhere/doing anything cool 😂 but when she was pregnant we started to become closer with her wanting a lot of advice about stuff like BF and home birth which I've got a lot of experience with having done it myself 3 times and also training as a midwife! And then after her and BIL split I was her main support. She was very depressed for a long time and I saw her several times a week, we did loads together and became what I thought were really good friends.
However over the last year or so BIL has stepped up (which is great, obviously) and now they have the DC 50/50 and SIL spends her weeks "off" partying hard and her weeks with the DC sending them to her mum so she can recover/work/go out more the weekend. She feels that she has finally got herself back after being lost in baby world for years.
Obviously that's her choice but it hurts a bit that she basically has gone back to considering me boring (she as good as says so sometimes, she can be quite blunt!). I feel a bit like now I'm no longer useful to her I've been ditched. I tried to say so to her, very gently, when I bumped into her at the weekend (mutual friends birthday where she made a comment about me being out for a change and trying to get me to have more drinks) and she had a go at me saying I only liked her when she was depressed. Which I suppose it must seem like to her? But it wasn't like that at all, she didn't have time for me until she was depressed!
Unsure now how to handle it, I just went home and cried a bit and tried to forget it but it's left me really hurt and doubting myself 