Would you do this?

I have a regular at a coffee shop I work at who is awful (but we all are nice to her and ignore it) today she felt ignored because she wasn't greeted immediately (the register girl was putting something away and didn't see her) so the customer called her a bitch. To her face. The Co worker is pregnant and was very upset. Then the customer called a sweet 70year old couple "stupid, why are they so happy?"and they heard and left. We filed an incident report, but were told to do and say nothing. I put in my two weeks earlier and have three days left, I want come back when I no longer work there and tell off that customer as a non employee (matter of factly, no threats.) Just so she knows what she did was wrong, hurtful, and she's a bully. Would you do this or ignore her forever? I don't plan on going back to the company, I want to defend the poor pregnant girl that was crying from that customer. Would you do it or no?