My sister just got banned from my house. She was hanging out with me, my husband, and our foster son. We had told her we are in the process of adopting and she was happy for us. She knows how much we want a family. She asked questions about his biological parents and I just said his dad is dead and he doesn't like to talk about his mom. She was very abusive. My sister then starts saying "Well does he know she loves him. She is just sick." I said "Idk, but leave it alone. He doesn't like to talk about it and I don't want him to be triggered". She starts to say "I just think its important for children to understand their moms always love them. They just make bad choices ". I tell her again "Look, just drop it, and don't say anything to him about it. I'm serious. It's not your place". I asked my son if he could bring the Kool aid from the fridge outside and he did. We sat and drank Kool aid and my son was reading a book. Then my sister asks how he feels about being adopted. He said he was happy and excited. She then says "You're not gonna miss your mom". I told her to stop right away and she says " I'm just curious. Aren't you gonna miss your mom". I see my son start to get anxious so he gets up to go probably to his room to calm down. My sister still won't stop " She did love you. She just made bad choices". He just tells her "She didn't, but thank you". She still isn't getting the message to stop and she keeps going and starts following him saying "Mom's are only human. They make mistakes". I'm tell my sister to shut the hell up and leave it alone. My son says "Yeah! She made it very clear I was the mistake she made!" He was starting to cry and shake so my husband took him inside. I start yelling at my sister and she said she was just trying to help him see from a different point of view. I told her she should have fucking left it alone. She said if everyone is gonna be mad at her she'll just leave and I told her not to come back until she learns what boundaries are. She's 30! She should know when a teenager is obviously uncomfortable talking about something. Especially if they're walking away. I told her from the beginning to leave it alone, but she doesn't have respect for me or my son to listen.

Edit: Thank you guys. I feel better knowing I did the right thing. My sisters problem is like someone else commented, toxic positivity. She believes everything can be better if you choose to be happy. She doesn't really believe mental illnesses are real. Shes also a "You have to forgive a person and see the good in them no matter HOW much they fuck you over" type of person. She believes everyone deserves forgiveness and will pressure you to forgive someone even if it's not her business. I didn't think she would ever go as far as she did today though. Especially since this is only her second time meeting my son.