I would say, only you can know that. How does she feel about gay or bisexual people? Would she feel disgusted or flattered? You could approach the subject by using a celebrity as an example, talk about their bisexuality, and see her reaction. You might know this already. But it will be a shame if she stops being friends. If you don't want to be active with a woman then it should not be a problem.. but only you can know how she will react to you saying you are bisexual.

I wish you the best of luck.