Hi Steve and Welcome to PC.

I have been subject to the rumor mill myself. Mostly in high school where this type of stuff is ramped. When someone spreads the rumor that your gay, it's most likely because they do not understand your decision to remain a virgin until your married. Also, in high school this is considered "juicy gossip". It doesnt make it right but people in high school are not thinking what is right. The same with the rumor of you liking boys. It's cruel and unacceptable. I'm sorry you had and still have to go through this. It's terrible and it really hurts because 99% of the time the rumors are not true.
As far as the lady at your work, I would take every precaution possible to avoid her and if you do have to have contact with her, make sure you have a witness. The last thing you need is someone making false accusations against you. I hope that this issue subsides for you. Again, I am sorry your dealing with this. Take care.