Prisca is a much better alternative, in my opinion. It's much less glitzy than Priscilla, which is almost gaudy to me, and the "prissy" connection is less evident. It shows more restraint. You'll also avoid the Godzilla association. I could see a girl named Prisca quite easily, but it's harder to imagine a parent naming their child Priscillam which seems more suited for one of those Persian cats.