My best friend is doing things that conflict with me morally, what do I do?

My best friend (and longest friend I've had) is really getting on my nerves with her behaviour and im not sure what to do. She was with this guy for two months and it didn't work out because he dumped her. It was pretty obvious that he was cheating (he never saw her, hardly called her, would disappear, added random girls to social media, would stay at hotels and not tell her, and he asked her to be official after only two dates!!) So they broke up and she hung out with him again and had sex with him. She saw his phone by accident and saw in his messages "babe" with a ring and heart sign; and a lot of other girls names under. She asked him about this and he said "I just put that girls name as that to impress her." Sounds like BS to me. When she told me this, she said she doesn't care if he has a girlfriend and that she could care less about being the other girl. It really annoyed me. She said I was being judgmental when i tried to say "what if she was in your position before and has no idea." She doesn't give a shit about sleeping around with a taken guy. I could not believe what I was hearing.

Now what really irritates me, is that her mom has MS and is really ill; and she lives with her grandma too. What if she gets covid? her mom would die. She is having (unprotected sex by the way) with a guy who is sleeping around a lot. I tried to talk to her about it but she said i was being really judgmental. This friend also has been really bitchy to me lately and makes fun of me calling me stupid. But i dont know what to do because I've been friends with her for ten years.

Any advice?
My best friend is doing things that conflict with me morally, what do I do?
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