Friend's birthday do, a girl I used to see briefly will be there, tell gf or not?

My girl mate is having a birthday do soon and has invited a girl I briefly dated (she left me for another girl, i know lol)

We never slept together or anything, just a few dates and stuff but should I make my girlfriend aware that she will be attending? My girlfriend won't be going. Or should I just be pleasant to this girl and just not tell my gf?

Put the internet to work for you.

via Personal Recipe 2629979