I'm so bitter and I hate it

Hi ladies, I'd love some advice in how to deal with my bitterness towards my sil. I hate her. I got with my husband about 10 years ago. I met her before I met him and she was lovely, we got in great, not friends or anything but we'd have some friendly chat it the pub. Anyway I then got with oh and she suddenly hated me. Over the years she's said nasty things, not really really horrible but just sly comments and then one day had a really horrible rant at me about how I was stealing her brother and I wasn't part of the family, in front of my oh who later just told me not to bother with her anymore and not to try and be nice because she's poison. She's gotten away with awful behaviour throughout her life because "she's got 3 big brothers and that's hard to grow up with" which I'm sorry but that's no excuse. Shes never had any female friends because she just ends up bekng nasty and until recently was a big loner. Now somehow she's met a fantastic guy and they've had a baby girl. She's 4 months. When pregnant everyone kept saying things to me like "God I can't imagine her as a mother" "could she actually manage" "will she raise her LG to be a witch to" to which my response was always "she'll be a fantastic mum, she's not what people think deep down" - I've never ever bitched about her to anyone other then my best friend, people have always tried to say nasty things to me about her but I've never let on how horribly she has treat me. Anyway, now she's had her daughter suddenly she's a wonderful mum and such a nice person and everyone thinks the sun shines out her backside and motherhood has totally changed her, which in fairness it kind of has, except she still will not say a word to my oh and I, she just flat out ignores us. My mil got really upset about the whole thing last year so for her sake I've tried to make lots of effort a to be at least on speaking terms but she won't have it, she won't ever look at me and I don't know what to do. I hate how everyone suddenly loves her because I still hate her for how she is with me. I know that's bitter and wrong but I can't get over these feelings, what do I do? I just want her to be miserable because that's how she makes me feel.