IT's OK to just feel the kneecap, but I can't think of any reason why she should. What I think is completely unnecessary is "mobilizing" the kneecap, which is something that many US PTs seem to think necessary. It isn't. The kneecap will gradually become mobile as healing progresses and swelling reduces.
I've had three knee replacements here in New Zealand, and spoken to several orthopaedic surgeons. No body here seems to think that mobilizing the kneecap is necessary.