Is OTHER wrong in the post ? POST : So, my friend, lets call her Annie, was dumped be her boyfriend, but after a conversation, they agreed to be in a open relationship.
She started using Tinder, something that i was already doing for some time, but i was not being lucky. Then she told me that she started talking with a programmer (i'm one too), and coincidentally i had matched with him too, but havent started a conversation. 

Annie was apparently very happy to hear that, she told me that all the time they were talking, she was thinking that he would be a good match for me, then proceed to say that i was perfect for him, that i should talk to him, that he was nice and all.
After hours of her insistence (I did not wanted to talk to him after she and he had talked and done well.) I talked to him, now full of expectations to finally talk to someone nice.


The next day, Annie tells me that she was going out with him, but just as friends. Me and her had booked to meet later, and when I went to meet her, they were making out. Next day she went to sleep in his home and fucked him. She told me that she does not intend to have a relationship with him, since she is already in one (despite having told him that she was single).
I have no intention of going out with someone my friend has dated, first because i dont feel confortable and i dont wanna to make things strange, and second because she has one very contagious STD.

I was really annoyed that she had created me expectations and then decided to go out with him, without any kind of warning. I had no intention of talking to him, but she pressed me so much that I decided to take a chance, only to later she go to fuck him. I dont understand why she did It, and i dont feel confortable talking about that with her.
I just wanted to feel happy for her, because she is having fun and feeling beautiful again, after the hard relationship that she is in, but i cant because i'm feeling betrayed, and i'm feeling very bad about that. AITA?