California - I'm thinking of pieing my ex-girlfriend in the face on halloween

I went through a nasty breakup and was cheated on. Basically I'm hurt but I still want to get back with class and humor. I was thinking of wearing a full costume and just making a whip cream only pie.

Is it against the law to pie someone in the face as a prank?

If so, what charges can I face?

Can I use my right to remain silent if somebody is trying to get me to admit to the pie throw because they cannot prove it?