What should I do about my sister in law???

She and my hubs brother have been married five years, that's after knowing him for 12. At certain times she has made it very clear, she does not approve of me, nor will not. I have known my hub 3 years, had sex before marriage (led to a miscarriage only 2.5 months), and because of that she told me I was a disappointment and she had to get pregnant so the grandparents could have the grandchild they had wanted. She tried getting our mother in law to stop him from marrying me at the alter, which mom in law told me about. Sister in law is currently 4 months pregnant and constantly asks me what I was like at that stage and goes, "ooh wait... never mind." She is driving me nuts, I can't be around her without wanting to cry, which is difficult because the brothers are so close. HELP!!!