Would you argue or let it slide?

I had a really close friend who I would come to for help whenever I had problems with my boyfriend. She knows my boyfriend as well, as I know her husband, so we had a really close connection from all our relationship talk. My boyfriend and I were on the verge to breaking up because we had been arguing nonstop so I went to her and told her the situation and was venting. She told me that I “should just dump him because we’ve been arguing too much” and “I don’t deserve all these tears, I deserve to be happy.” And y’all know how relationships are, it gets ugly at times, but they can always be fixed. So me and my boyfriend are all happy now, talked things through and everything. So I was at work and when I come back to my boyfriend, he tells me that she had DM’ed him. She told him that I told her about the situation and that she wants to hear his side of the story. He replied to her saying that’s none of her concern and then she said that if I stress him out too much, they can go out and talk about it. She was telling him that they should go to Six Flags and spend the day together. He told her that she should go with her husband and that he’s not interested in going out with her. Before she replied, he blocked her. I realized it was my mistake for trusting her and communicating with her instead of him. But seriously like what the fuck? Going behind my back and trying to take my boyfriend out on a date? And she still has the nerve to DM me after and ask me how I’m doing. I really want to pick a fight/argument and tell her off but I don’t know if it’s worth the time and energy. Should I just cut her off and move on? What would be the right decision?