I agree that it is not your fault that you have fallen for her. You can't help who you like or love. I also agree that it depends on what you do with those feelings that will make people question your character (how good of a friend you are).

You should not pursue her! If she becomes single, that may be different...

__________________

If a raindrop was a kiss, I'd send you a shower.
If a hug was a second, I'd send you an hour.
If smiles were water, I'd send you the sea.
And if love was a person, I'd send you me.