Well she may indeed be someone with a personality disorder. But just saying, their history was seriously challenged by medical problems, correct? So it might be a good idea to work on a somewhat more compassionate view of her - even if she's awful - for your own sake. You of all people have it in you to do that, as you've proven in your relationship with OW and exH. It's never a good thing when the new partner gets all into defending their partner against the "horrible ex" - he married her and had a child with her, and it won't help him for you to get involved with being mad at her. Of course she's going to be jealous of you step-parenting her son, and likely jealous of her ex for having a happy relationship with you.
Also - if she IS someone with a personality disorder - you need to be strategic. Hold your friends close and your enemies closer kind of stuff.
