No I'm not.
First the ACLU says to ID yourself so as to avoid hassles. They said the arrest may be illegal - and it would be in CA if the officer lacks reasonable suspicion. btw illegally arresting someone can open the officer personally to a lawsuit under Federal law.
According the Supreme Court anonymous tips are generally not good enough, even with a description, to stop someone. The SC in Florida v J.L found that a anonymous tip that said a "young black male in a plaid shirt standing at a bus stop" had a gun did not on it's own give the police justification to seach the man.
There's also a specific California Supreme Court decision (People v Wells) that basically says uncorroborated anonymous tips only give reasonable suspicion in cases of grave public risk (in this case it was a drunk driving stop). That's a very narrow reading of the Supreme Court ruling that would probably get tossed if someone challenged it but even here there needs to be a grave public risk. Watts doesn't come close to what anyone would call a grave public risk.
What I got wrong was that the Watts call wasn't anonymous. If it had been and if the cop didn't see it he could not legally ask for ID and she would have been right to refuse it. Sure he could have arrested her and complying with the request may make sense from a "I don't want to be hassled" standpoint but that does not make it legal.