What can cause my 7 year old girl to have hearing loss she had it in left ear dr gave her medicine its getting better but now her right ear has it?

Probably ear fluid: Did your daughter have an ear infection and antibiotics helped it resolve? If so, when the worse ear resolves, the less affected opposite ear can be more prominent.

Likely otitis media: Otitis media is a condition typically characterized by the buildup of fluid behind the eardrum in the middle ear space. This condition is quite common in children, with decreasing incidence as eustachian tube function improves with increasing age. If your child had a cold, it's quite possible for her to have one ear affected followed by the other. See ENT if symptoms persist or recur.