Pseudonymph (adj.)- any girl who pretends to want you really badly. She may even do inappropriate things in public. But when you finally get a chance to get in her pants, she is a total prude.
Dude1: Dude, that girl at the party last night was all over you, I think I even saw her grab your junk. Did you give it to her?
Dude2: No dude she ended up being a total pseudonymph. I brought her up to my room and she just sat on the bed and wanted to talk.