I found this possibile answer online.
So- is it just the hair on the ground you have noticed or can you see bald or thinned patches on her body? If it is just that you THINK she is losing hair (and can't see her having bald spots etc) how are you sure it is not normal? Does she have long hair and your opthers have short hair? Different breeds will shed differently, some may shed rapidly and some more slowly. Is she the same breed as your others?
However,. if you cabn see patches of thin or no hair then it is probably a condition of some sort. Cats can display what's known as "excessive bathing" when stressed or ill. Basically they spend so much time grooming, they lick the fur out. However this tends to be swallowed so you don't notice it on clothes etc, I noticed it on my cat when the backs of his legs looked like they were going bald.
If there is no reason why she might be stressed or ill, it could be something else like an allergy or some kind of infection. Have you checked her for a fungal skin infection such as ringworm? Or a parasite like scabies (mange)?