Oh Guru Boleslav, I need guidance.

There is a girl on my floor in my apartment building who I'm pretty sure keeps flirting with me (She gets all blushy, says things like "Hello" with a shy grin, etc. etc.). But on the other hand, I am sort of in a relationship with a woman who is insanely desperate and clingy (the sort of woman who says she wants to have your kids after the first week.). And on yet another hand, it looks like there may be an upcoming opportunity to get back together with one of the few exs I still speak to.

Oh Guru Boleslav, please guide me.