Similar situation happened with me, my ex and her best friend. She got a new guy friend, I knew he liked her and she denied it. Things started to get weird, he became very needy/pushy, stepped on our boundaries and she was still in denial. I told her to distance herself but she refused and their friendship grew stronger. He told her he liked her, she pretended to not know and told me a whole month later. He then tried to get her to break up with me, and she told me that she was going to distance herself from him this time but didn't. I put up with it for a very long time until best friends guy friend also caught feelings for her. He told his friend to back off, but he doesn't, then proceeded to tell her to not be the other guys friend and she agreed. She blocked the other guy from everything in a heartbeat. When I confronted her about it, she told me that the scenario was completely different. We broke up a week later. She says she loves me and still wants to be with me and doesn't understand why I thought that she chose him over me.