A responsible owner will have its dogs neutered. If an owner prefers not to do this, the ONLY way to prevent mating is to isolate the female when she is in heat and not allow her to be anywhere near...
A dog may try to mate with you because it 1:loves you
2:is deprived
3:you may be wearing an article of clothing that is appealing to dogs
4:it is trying to dominate you
I don't know if you can stop it, but to keep her from damaging her bed put down an extra sheet or blanket. She is probably trying to make a nest, but cant because that material is attached to the dog...