Most Helpful Guy
Not your fault. Some people are users. The best solution is to learn from this, and not let people abuse the friendship and trust you offer.
Best option is that you won't even dignify her comments with a response. I have a "friend" who constantly badmouths me. Calls me some really nasty names. I don't respond. Now, some people might think of that as "wimpy" - I'm not defending myself.
But I see it as fairly smart, and a way of "turning the other cheek." I don't stoop to that level. 1) Every time he's nasty to me, his stock goes down a little bit more. 2) It makes me less likely to get hot under the collar and say something horribly nasty, and keeps the real estate in my head dedicated to him relatively low. He calls me all kinds of names, but I know that I'm not any of those things. I've proved it time and time again, that I've been the more genuine friend to him than he has ever been with me.
So... best advice is to move on. Go "ghost" with this former "friend" and don't dignify her petty behavior with a response. Don't let her in your head.
You can only defend yourself by being a great person and showing it. That is your greatest response.
Most Helpful Girl
You didn't do anything wrong here so I don't understand why you feel horrible. She is the immature one who is at fault. There's nothing you can do but put this entire friendship behind you. It's not worth anything. I understand you want her to know that what she did was wrong but I'm 99% sure that she already knows this and you crawling back to her is going to probably just amuse her more than anything. She knows what she did and she doesn't deserve any more words from your side. She sounds like a very creepy person and you should be happy that you got rid of her. I think she would have ended up being a very bad friend to you in the long run. As for whether you commenting on her gf would be enough to ruin a friendship.. you are absolutely right. My best friend would never end the friendship just because I expressed the fact that I didn't like her partner. She would likely be concerned and listen to my opinion. Same if a friend did that to me. If someone I cared about came to me and told me they thought I made a poor choice in selecting a partner I would genuinely be concerned and wouldn't end the friendship just because of that. She obviously had a hidden agenda all along and it's time you forget about her and all the sadness. She doesn't deserve a good friend like you.