Niece with dead bf’s husband.

My niece’s bf died of cancer. Three days after she died, her husband said to my niece that “now we can be together’” My niece was horrified that he said that and said he had been like a brother to her. I told her to stay away from him. Two weeks later, my niece tells me she has been talking with him and they were helping each other to get through their grief. I asked her how could she do that after what he said. She didn’t have an answer. Two weeks later, she tells me she is with him. She has been married four times already. We started to have a bit of a heated conversation, and I ended up telling her that they were both doing her friend wrong. She tells me a few months later that she is really happy with him and that I’m the only one that has a problem with it. I am not the moral police, but it was way too soon! But the main problem I have is with what he said to her. I think it is creepy. I love her unconditionally, but I’m having trouble with this one. About five years ago, she let her son go live with his dad, so she could be with a man she ended up marrying for two years. She would not talk to me during this time. Her son still won’t talk to her. I told her she needs therapy. We eventually got close again. We barely talk now which is sad because we were really close. She is sweet, funny, caring, and we have a lot in common. She was named after me. Should I try to repair our relationship, or should I keep my distance from her?