Does she actually know you care about her? If you have future plans which involve her, you need to include her in the planning. If you don't, then yeah, she won't know wtf is going on and could end up with some other guy, a guy who's actually told her that he cares.
You don't need to give her a big love confession to start. And, in fact, that's not a good idea at all. More like you say to her, "Monisha (or whatever her name is), I have been thinking about you and me. I mean in a romantic sense. Do you feel like I do at all?"
And see what she says.
It would be a shame for you to change your life to suit someone who already has a boyfriend and/or doesn't think of you that way.
And yes, do this. It's kinda mandatory. The way I see it, you've been hemming and hawing for over a decade.
If you don't tell her, there can't be a happy ending with her.
And yes, that's a risk, and risks are scary. But daring and trying is far, far better than never trying at all.