I think I know I'm being a bit touchy about this but need outsider perspectives. I went low (strictly necessary only) contact with my in laws after years of them being (well, what I consider) awful to me. I don't see it as my job to facilitate DH's or DC's relationship with them anymore, DH can do that. I've blocked them on all channels but DH keeps in touch. Neither me nor DH are on Facebook.
My sister is younger than me, slim and absolutely gorgeous. This year on her birthday she took a fabulous photo of herself and presumably put it on her Facebook page. My MIL screenshot it and sent it to DH saying "have you seen this?" To not drip feed, my sister was on roller skates in the pic so not just an every day photo. The only reason I know about the photo is because DH said "have you seen this?" MIL has only met my sister a few times at family functions, so I have no idea why she sent it?
AIBU to be a bit jealous? I actually don't know.