If I could offer some advice, I think if you walked away from the table you wouldn't be losing anything from it. She's not treating you like you deserve, and she'll gain a new respect and appreciation for you if you decide to deny the terms of the relationship that she's set on you. I dunno, just something to think about, but it's harder to move on if you're still connecting with a person. Plus, saying "no" to being platonic is sure to make her re-think things if she's even half-way interested in you romantically. There's a lot to be said for "you don't know what you've got til it's gone." You don't apply any pressure on her to leave the other guy, you just say "this no longer works for me, but if you're ever available give me a call because I'd totally love to see you, just...not as buddies." If you stay centered, and charming, and understanding, but assertive, it goes a long way.