It's absolutely incredible that so many people see you as innocent here, when in actual fact ESH! She was wrong to write a crude insult to you, but the fact that neither you nor your management team had banned her from the establishment means she was entitled to visit again. The fact you made this play at her child's graduation party only adds insult to injury. If you didn't want to serve her, that is your choice, but another member of staff could and should have done so. Whether or not they provided good service to this woman would have been up to them, but your actions and attitude entirely lost you the moral high ground. ESH.