AITAH for telling my friend her boyfriend was hitting on me?

I (19F) have a friend, Alyssa (22F), who’s been dating Mark (24M) for almost a year. A few nights ago, we all went out to a bar. At some point, Alyssa went to get drinks, and Mark stayed behind with me. He started leaning in really close, telling me I looked “incredible tonight” and that he always felt there was something “unspoken” between us.

I told him he was crossing a line and walked away. The next morning, I texted Alyssa and told her exactly what happened. She called me crying, but then she started accusing me of trying to ruin her relationship or make her jealous. She said Mark would never do that, and that I was reading into it because I was “always single.”

Now a few people in our group are saying I should’ve just kept quiet because I don’t have any proof, and it’s just going to create drama. I honestly thought she deserved to know, but now I feel guilty for getting involved.

AITAH for telling her?