Hmm, why does everyone call Erin cheap or slutty? There is SOME evidence with the favorite things bit describing her favorite as "bondage." But Alan not only called her "trailer cheap" and brushed her off with "I like girls with a little class" in Absolute Beginners but "pure as the driven snow" in Painted Moon? And if I remember, Bleu was telling her "Unlike some people named Erin, I have some respect for myself and know what modesty is!" and "Big deal, she only shaved her legs! I would have put on a REAL show!" And I think there were a couple things in Lovecats and PM.
She also seems a little bit of possessive of Bleu in spite of her trying to ruin her love life.
But I still think she'll end up with Monkeyboy and can't wait to see what she's got for everyone in Thieves Like Us.