Step Down Bitch?

There’s this woman who’s completely fabulous. She and I are often attracted to the same men, and it’s proven to be slightly awkward at times.

My question: what is the etiquette for hitting on or moving forward with the subject of our mutual affection?

Here are a few things to consider:

- The woman who admits having a crush on the guy first lays claim to him?
It’d be awkward to follow her comment with a, “oh I have a crush on him too.” And if I did say that, then is the competition on? I know I’d feel guilty (that fucking guilt complex of mine) if I got him, and she was completely bummed.
- Are there lines, like if she only has a mere crush on him it’s okay? Or if she’s just kissed him once it’s okay? What’s okay?

My younger sister, Snot, ran into this issue over the summer. Her friend shared an apartment with this guy (a friend of a friend kinda’ thing)… Snot met the guy through her… the three of them hung out all summer… her friend confided in her about her crush on the guy… at that time my sister had developed a crush on him too… Snot didn’t mention it because she didn’t think her crush would amount to anything, and she didn’t want her friend to feel competitive… but one night, Snot and the guy made-out… the guy wasn’t into her friend… After that happened, my sister thought it appropriate to discuss this to her friend… the friend was pissed.

What would have been the right thing to do? Two people shouldn’t try out a relationship because they want to spare the friend’s feelings?