Your neighbor has begun to let the public have acces to a private gated parking area on her side of a shared driveway can she do this?

The answer all depends on the language used when the shared driveway was created and state laws. It also depends on where exactly she is providing access, over the driveway easement or on her own land. If the land involved was specifically dedicated to a "shared driveway" to be shared by the owners of the abutting properties then she has no right to put the land to another use. You should consult with the attorney who represented you when you purchased the property. Shared driveway easements are an unending source of trouble when one or both owners overstep their rights. You need to check the language in the deeds and determine what state laws govern the easement. For that you need expert legal advice. You should act ASAP.