Consider also that what is crushing you is not so much unrequited love, but that you keep the feelings for her inside yourself and she does not know.

If you tell her and she doesn't reciprocate, you may feel weight off your chest because at least you have expressed your feelings. And there will be less uncertainty and ambiguity. People in general find dealing with uncertainty difficult.

Also, if you tell her and she does not reciprocate, then you will be well within your right to call your love unrequited. At least you will earn that important right.