Annoyed and depressed (long)

Ok so i will start this out by saying im very happy that my sister is pregnant, and i know she doesnt really have anyone to talk to but me. Im just really annoyed and depressed because this is her 5th pregnancy.. She has two kids already, 2 and a half year old girl, and a 1 and a half year old boy. She got pregnant twice last year with twins 2 times and each time she got an abortion. (please no comment on the abortion), and will probably get another abortion this time to. I tried to tell her my husband and i wouldnt mind adopting the baby, but she says she would rather get an abortion rather than give it up. my husband and i have been trying for 3 years now to have a baby and no luck. I have no one to vent to because i dont have friends. I feel lonely and depressed all the time because i would like to have a baby with my husband. My husband has a son, whom we rarely get to see because if his mom not liking the fact the my husband married me and not her, (shes told us a few times) and i have a son from a previous relationship whom asks me almost everyday for a brother or sister, i also have a daughter who was given up for adoption, because of her dad. I just dont know what to do.. I want to be here for my sister when i know she doesnt have anyone to talk to but i dont because it depresses me badly. I have asked in the past for her to not tell me that shes pregnant but she just doesnt seem to care. I have blocked her from.facebook and from being able to call nd text me sometimes because she just doesnt stop. Idk what to do. Any advise!!