My crush says she likes me, but is dating another guy. I told her she was in a relationship, and she said that she would consider dating if/when they broke up. Advice?

This remind me of a customer trying to buy something and considering his options to catch the better product with reasonable price.

You can keep being friend with her but don't consider her as a relationship goal because the way she carry the values are so low and inappropriate.

Just take a deep breath.

Then listen to Bikergirl.

Run away!  You are definitely not a priority in her life.  Go out there and have fun until you connect with someone who values the relationship as much as you do.  Don't be a standby option for anyone.

Talk is talk..... Her actions say more then her words. You are setting yourself up for a heartache. :0(

Matt is right..... Listen to BikerGirl!