What should I do?

Katlynn🐢
I was pregnant back in October and I was told it was a molar pregnancy so I had to have a D&C done. I was not supposed to be pregnant for an entire year. 6 months later I found out I was pregnant again and even saw the baby at 6weeks. But the doctor told me I would miscarry because my levels were low. Now I'm 10 weeks and heard the heartbeat already. I'm excited but my sister in law is causing all types of problems. 
   My fiancées sister and his brothers girlfriend are both pregnant right now also and his sister is making a big deal about my pregnancy because of the risks since my molar and my misscarriage. She is always making snide comments about how our baby won't be healthy and have tons of problems. She is always commenting on the fact that we are both just 19 and not old enough. 
What she doesn't realize is yes I know that I am putting myself in danger with my pregnancy and it's not like we planned this. I may have had a molar pregnancy but I don't need her to make her comments about my unborn baby. And she needs to realize that she is putting herself in just as much danger with her pregnancy from having two abortions and getting pregnant right after the second.  
I can't keep my fiancée or baby, when born, away from his side of the family but I don't know what to do when his sister starts her comments and bitching. 
What should I do?