So a bit of back story here. I 27F have been friends with a guy 29 M for about 12 years. We have been friends through every heartbreak, when I became disabled and everyone left me because I was no fun anymore, he stayed and would always be there if I needed him. I give him advice, he gives me advice, basically we are just best friends.

For this issue we will call him A. So A started dating someone a few months ago that we will call S, S is 21f. I am somewhat friends with S, they have helped me when my mental issues have gotten bad. But at the beginning of their relationship I have always told S that A is my best friend so if there is a fight I will be on A's side unless he did something really stupid.

They had an argument and A was feeling pretty shitty over it and didn't know what to do. S started venting to me about it (never saying not to talk to A about it, because if she did I wouldn't have let her vent to me). I decided to give A some advice (not telling him exactly what S said to me but in a roundabout way trying to help), he was thankful for it because he really didn't know what to do. And I knew I needed to help my friend because he was hurting.

Something about me you should know is, I can't just hear a problem without trying to fix it.

So after talking to A about everything and getting him to where he is comfortable dealing with it, S is now mad at me that I talked to him.... Saying I am a horrible person and I had no right to talk to him....

I know I should have just kept my nose out of it and told S that I wasn't the person to vent to and gave A whatever advice I could without knowing what it was, but I honestly was just trying to do the right thing and help my friend that was hurting. So AITH?