Okay, this idea is not not foolproof but if you feel strongly...
Gather up all your past performance reviews, since you are friends I can only assume they glow like Chernobyl.
Then wait for your next review, again it will glow like a camp fire!
Then wait for her next anti-semitic remark-- I doubt with a bigot it will be a long wait. Bring a tape recorder to the meeting, though I'm not sure that's legal, get advice on that.
IF she fires you, you have a lot of evidence as to the real reason she fired you, not poor job performance, though she may not use that excuse.
Find a nice Jewish lawyer (that's a joke!!) Being served with a suit from a Jewish lawyer will give her some nice arterial fibrillation!
One day whatever you do, you probably won't know this woman, but you will be stuck with yourself forever.
If you don't do this, look for a new job but contact a Jewish rights group and out her, hopefully the Jewish customers will leave, and word will go out.
Of course a lot depends on your circumstances--weigh them carefully.