The title already makes me seem like a major cunt but hold on. Throw-away acc btw.

A few weeks ago I broke up with gf and this specific moment came to mind. On our first date as an actual couple, we were talking while she was sitting on my lap. We were making out and talking about life when she starts to talk about her recent trip to disneyland, how it went and how good it was. It was all fine until she started to talk about a certain guy, saying he was "the best one week bf I've ever had" and that they wanted to date badly and would be a couple right now if it wasn't for the fact that he lived in another state.
She just kept talking about him and how good he was, how she liked him and that they dated for that week and still talked to this day.

This got me unconfortable for obvious reasons and I really disliked the whole conversation. I changed subject quickly after she stated that she still wanted to date him and didn't think much of it. She then grabbed my phone to see how many messages we have with each other via WhatsApp and stumbled upon a certain number from a friend. The number was saved only as "Hummingbird" so she clicked on it and saw that we had 15K messages with each other. She asked with jealous tone who it was, to which I answered "Ah, it's just an old friend that I once had sex with in a bathroom, crazy stuff." She quickly changed subjects after that. So, AITA for doing this as a petty and harmless "revenge" on her for making me listen to how she would date and fuck another guy if he didn't live so far from her? It's been bugging me this whole time and I want to know, some people say I am, some don't but I really don't know anymore.