Absolutely stay away from the L word. Burned me a couple times even though it was true. If things take off you'll know when to tell her that.
Another thing: if you've been thrown into that friend category you can toss any hopes of getting into the sack right out the *******' window. Once you're a "friend" it's damn-near impossible to get into the "potential Uck-buddy" category.
I see where you're coming from, though. If you two have known each other for so long it's kind of awkward to ask her out...but that could be a stepping stone around her current boyfriend. So is she "in love" with this other dude or what? This'll make or break your chances and also modify how you can go about getting her to be your girl. I think you need to play it cool if you're going to win her over. She's going to get lonely (THIS IS A SURE THING), which will be more of a burden than anything on her. Don't push, just be around to talk with and know when to leave. Pushing will just make it blatently obvious what you're trying to do, then you'll lose a good friend.
Mercury had a bunch of great pointers. Remember I said pushing will make it blatently obvious? Same thing with the way you look at her and your whole body language. Women see right through it somehow. I wouldn't go over with expectations of any kind. Just go equipped with the way you feel but be careful in the way you present it. Again as most here have said, listen to what she says and WHEN she says it. Know what I mean?
If she starts talking about the boyfriend, don't flip out. Just act interested for a second. Be like, "oh really?" You might wanna bring up some old memories of school together if it goes that direction. Good luck man. Hope things go your way.
------------------
Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch