Well, what's the worst that could happen?
Let me tell you a story.
I met this girl in a college algebra class. Pretty much the polar opposite of each other. I'm quiet, she's loud. I'm olive skinned, she's white as a sheet. I'm an introvert, she's a big extrovert.
After progressing from helping each other with homework to hanging out, things start getting interesting. We have some drinks together, she meets some of my friends, I meet some of her's. We jokingly wrestle on the floor one day. (She was Bisexual and played on a women's rugby team...the kind of lesbian who is the adoration of the other lesbians because she doesn't look like your stereotypical lesbian. Anyways, she liked to play rough.)
I start spending a lot of time with her, like a couple hours a week hanging out. I meet her family more than once. I manage to be there for her when "real life shit" happens and she gets her collar bone broken during a rugby match. I'm the one she turns to, to take her to the hospital. We talk about sex, what we like, what our turn ons are, all that stuff. By all rights, I've been both a good friend and a decent prospect at a romantic interest.
At one point when she's getting all flirty one night, she shows me the color of her panties. All the while giggling like a school girl and her face redder than the color of her hair. I mean, that's pretty much the go signal for any guy. No booze for either of us, just sexual tension.
So finally, I can't take this shit anymore. The flirting, the ambiguity, and I just pop the question that night while we're sitting out in her car smoking (I was staying at the dorms at the time.) "Do you want to go out?"
And in a big hurry she says no and like that, the mood balloon is deflated. That was pretty much the end of the relationship. We hang out a little more, eventually go our separate ways, she ends up marrying a woman. Ran into her at work a few months back actually, as the woman she married is a sister of one of my coworkers.
Not by far the biggest embarrassment of my life, and frankly knowing where I stood was better than continually feeling like I was being toyed with because she was a tease in a lot of ways. In terms of reframing, as one of my friends put it "Dude, you almost made a lesbian consider going straight."
The worst that can happen, honestly, is that the people you choose to confide in give you shit for it. Maybe your relationship with her alters some because she's turned you down and either you or her can't move beyond that. As for "MOST CRUSHING EMBARRASSMENT EVER", it's a load of crap. Take a read on what LB said about confidence. It includes when you're shot down too.
Have no shame, as I've heard it said. If you have no shame, you have nothing to worry about if she says no, and everything to celebrate if she says yes.