SIL wants me to talk to my husband for her. I think he needs space

My husband is very upset with my SIL. She overstepped some boundaries but I do believe she did it with good intentions. His sister send a TT his ex wife made. There are three people we do not talk about. His ex wife, her brother, and his mom. The TT was his ex wife saying how her ex husband got HIV from cheating on her and talking about karma. My husband is HIV positive. He did cheat on her in the beginning of their marriage. He had told me that in the beginning of our relationship. They were extremely young when they got married. Not saying that as an excuse but he was practically still a kid. That is NOT how he contracted HIV. He didn't get it until several years later after they got a divorce and she and her brother broke into his home and she had her brother assault him in front of her. They both served time for that. It's not false. It's not a rumor. It's legally documented. The brother was already HIV positive. My husband is non detectable which is why I never got it and our two kids never got it. He had told his sister to ignore it. The TT barely had 300 views anyway and he doesn't care what she has to say. His sister made the decision to stitch the ex's TT and blast the correct information about what she did. My husband was really upset about this. It just caused a bunch of trauma all over again and he did go off on her for doing this. She reached out to me begging me to talk to him for her because he blocked her. I told her I think he needs time. I do believe she was well intentioned and thought she was doing good but she overstepped. I don't want to tell my husband anything while everything that happened is still fresh. Is this the right choice or would you try to mend their relationship?