Well---------if you're telling the truth, her calling you suggests she's a druggie and saw you as a soft touch.
She made the meeting, got the cash and then fucked off with her dealer pimp.
She's on drugs, probably gang linked, and YOU need to get your head in order and walk away otherwise you're likely to be in the shit with the dealer. You say you know her - does she know where you live?
And FFS don't go round debt collecting - too dangerous