We were going out for around 6 months. She cheated on me initially, cried about it a lot, and I forgave her (genuinely believing she was sorry, and this was quite early on). We had a month break from each other a month or so ago, until (she partially convinced me to) I paid for a rather expensive holiday together to work things out. I now find out that she is cheating on me again (at least 3 other guys on the go), has slept with at least one in a hotel room I paid for, and is openly talking to her friends about cheating on me. She still swears to me that none of this is happening, and happily takes everything I threw at her (since I'm the only one with a job).
She's over this weekend, but I don't want to just break up beforehand and feel like she's gotten away with all this. Am I justified in taking any kind of revenge on her?
I considered telling her mom what she's been up to (she regularly begs her for money to 'get to college,' which she spends on drinking). Alternatively some form of public humiliation, or a simple dine and dash might make me feel slightly better. We don't have enough mutual friends for them to have any impact on her.