AIBU pregnant SIL

[MarbleBarbie]

Basically (long story short) my SIL and I have a long history, she's hated me for years but I wasn't really very upset at first as I didn't see her very often and she spent a full year ignoring me. My DP is very supportive of me as they've never been close (he actually told me she wouldn't like me but not to care). Me and her are very very different but tbh that didn't bother me until I found out she'd been slagged me off a lot to anyone who'll listen even lying about things she's done but saying I did them. As I am the one who has come into her family it's made things very difficult as people have an idea about me before meeting me. She's thrown plenty of temper tantrums over things in our life that has nothing to do with her, DP and I have always stayed strong together (which ticks her off even more!). I've been told by a lot of people in my life as I have relayed stories she sounds jealous...

Recently she's fallen pregnant with a man she hardly knows and she can't stop rubbing it in my face. She's openly said she wanted to be first, that we should have to wait for her, she's even taken our baby name (a name me and DP discussed and said would be our child's name) because she got their first (prior to being pregnant had never said she wanted it, my partner and I are due TTC later this year as we planned years ago (we have always had a plan since uni) but she doesn't know this. I'm really worried if we do fall quite quickly (hopefully we do) it'll set off another tantrum and make things unbearable between her and her parents (they always side with her, no matter what)...

Just need some advice on how to handle her?

[SquinkiesRule]

I wouldn't even buy the pet to name, just find a pic of something she will really hate and post it with our new lizard or whatever, with the name attached. Let her cause all kinds of commotion whining and being dramatic in the family and sit back and laugh.