I Need to Vent

My ex-boyfriend and I broke up last week but agreed to keep being friends. We really haven’t be talking much, but today he decided to randomly send me a picture and snapchat video of some girl that he apparently likes. He kept going on and on about her all day, about how pretty and nice she was. I didn’t say much, just gave a few one-sentence replies agreeing that she was beautiful. I don’t know if his intentions were just to make me jealous or if he’s just trying to be evil. I’m annoyed and a bit hurt that we’ve dated since June and he has apparently moved on so quickly.
The girl is really pretty, and if they like each other then I’m happy for them. I don’t really feel like I’m jealous of her. I’m just more annoyed than anything.