<human>: So my girlfriend and I have been going out for a little over a year and a half and we have a great relationship. She is witty, ambitious, and sensible and I always feel happy when I am around her, even if I've had a shitty day.

I know I am a jealous guy and I've been a little jealous in past relationships, but it hasn't been a problem with my current GF until now. A few weeks ago she mentioned that she had just gotten back in touch with her high school boyfriend Dave after not speaking to him for years and that they had a nice talk. Okay, no big deal.

But she talks to him practically every other day now. They both play this online card game and she calls him her "game buddy." I trust her, but my feathers are ruffled from this behavior because I have never kept in contact with any of my exes, and I wouldn't if the opportunity arose out of respect for my relationship with my girlfriend.

I think she has noticed that I get jealous when she talks to him because she told me I have nothing to worry about and that it's perfectly friendly. She even gave me reasons why she would never be attracted to him (admittedly because I was sulking a bit...). They went out when she was 15 and she's matured, he does drugs these days and she is very anti-drug, she even wanted to break up with him towards the end of their relationship. All this stuff makes sense logically, but I can't stop feeling bothered whenever I walk in and see her playing that game. I don't know whether I am overreacting or if it's really inappropriate behavior on her part. Help?

Could you distill the essence of the text into 1-3 sentences?
<bot>: Girlfriend starts talking to ex-bf regularly, says that there's nothing to worry about because she would never be interested in him again. Still feel jealous whenever they talk.