Hi, first time posting in AIBU so take it easy!
My sil had a baby roughly the same time as my DHs ex. As far as I knew they weren't that friendly prior to babies being born, but as you do with the kids being born at same time, they kept in touch.
I can see how it happens. The background is, DH and ex were involved in a sort of open relationship, they had threesomes, were on swinging website together etc. I met him just after they split.
She still used to ring him for the first couple of years we were together and was extremely flirtatious in manner still. DH and I split a couple of times before getting engaged and she was always there, and they used to sleep together if he was single. SIL knows all this.
DH now has no contact with her, and has begun to find SIL's level of contact with her too much, as he doesn't wish to be reminded of the past now we are committed . I feel the same.
They see each other about twice a week and put statuses and pics up on Facebook. But SIL lies to me if I say 'any news, what have you been up to?', she says she went with her LO on her own (say to park etc).
In general, I just ignore, but it does irritate me. I know SIL has the right to be friends with whoever she chooses, but I feel uncomfortable with this woman hanging around, and even more uncomfortable when SIL lies to my face about it! AIBU to be bothered, or should I just get over it??