Don't get me wrong this is incredibly frustrating however people need to remain professional otherwise it only reflects badly on you otherwise.
Sending invoices, small claims court etc etc. All makes sense and is the right thing to do, heck even if you went to a fitness boot camp of hers and walked off without paying MAYBE you'd get away with it but than coming down to her level won't help and she could then go bad mouth you to everyone bringing bad attention to your business.
As for publicly shaming her with reviews etc, it's totally unprofessional and unethical and looks worse on you than her. You're potentially showing your professionalism to 5,000 of her friends and bad mouthing spreads quick. It's not worth the hassle to be totally honest.
Chalk it up to experience in my opinion. I've had clients go AWOL owing £££'s and most the time it's too much hassle to chase.
I totally agree but I don't think she should get away without paying, hell, if everyone did that I wouldn't have a business!