My gf has a crush on a guy, any advice? am i overreacting?

[vinny]

I've been in a relationship my my gf for the past seven years. During the 3rd year i had to move away to further my studies and im still away doing so. i travel back home every summer and meet up with her and spend time with each other. she recently took up a job in her country (sept 2013) and since then things have been rocky for us because when she comes home she is tired due to the long hours required at her job (especially since she lives far away). We got into an argument and she told me that there is a guy (who is a foreigner only working temporarily at her job) in the in particular who is a colleague of hers at her job who she talks to and she wonders what'd be like if she is in a relationship with him and how he would treat her. The guy has no idea (according to her) and she just finds him attractive because he looks like me.
Now bear in mind that she just told me this today and before that she went on a vacation with her other colleagues (of which this guy also went). Plus she encouraged her parents to carry her and the guy and another female friend of hers to do some site seeing around the country (because he was curious). She also 'likes' his pics on fb. I've posted a few romantic things on her wall and she doesn't even like them. In addition to this the company that she works for provides transportation after work to do extra curricular activities such as dance class of which her colleagues (including this guy) and herself partake of. ive spoken to her about it and she says that she cant help if he goes to dance class with her and vacations. And at the end of it all she comes home saying that she's tired and just wants to sleep and behaves grumpy. Please note, by nature im a very jealous person. am i overreacting?
Any advice is appreciated.
Thanks.

[Rowen]

Duplicate thread.