Crappit - wrote you a response but work computer crashed - will try to repeat it here:
First of all we're all nerds here and that means you're pretty much guaranteed to get the wrong answer because hey, we're nerds. The reason "telling her what you feel" will not work is that she's gotten used to unloading her emotions on you - it's like she's been airing her dirty laundry in front of you - something she would never do if she was interested in you romantically. You're basically asking for her permission to take that emotional support away from her - of course she's going to say no. I guarantee you will get the "I like you as a friend speech".
You're in friend zone if you're having deep conversations more than once a week while you're not in a relationship with her, so what you need to do is make space between you to get her out of the habit of unloading on you. Avoid her for a while, and keep unavoidable conversations polite and brief. When she asks you why you've changed, have a face to face conversation and tell her you like her BUT (this bit is critical) you realise she's not going to think about you in that way while you're seeing so much of each other as friends. You need to walk away first - it shows that you understand delayed gratification - that's a sign of maturity. If she volunteers that she'd like to try being romantic (only IF she volunteers), then tell her you'd like that, but still walk away. Call her to ask her out - but make a point of doing stuff you don't usually do, and don't allow the same patterns of emotional unloading to start up again.
If she doesn't volunteer anything, it's still best to keep making space between you. If you're good friends, you can still catch up, but do something that you don't usually do together (eg. coffee, concert) and keep it to once a week. If you like, tell her "it's not a date" with a wink and a smile, but eventually if you are clear about what you want, she will eventually decide one way or the other - and trust me the pain of rejection is not as bad as pining after someone without knowing.
Last thing is - don't talk about the other guy, if you try to sabotage what she thinks about him, it will almost definitely backfire and you will lose her respect. Just make yourself better in her eyes.
