I don't know whether or not she used the dark net but she was stupid enough to use one $20 bill at school and told the police that she can't remember where she got it. The police said they sent the bill to the secret service and, being at the school, they have all her information. No other bills were found but the police mentioned using DNA analysis (check if only all known people have touched the bill). Will she be investigated by SS agents at her door. What's a good defense for her, if you've had a similar experience?
But she got that back in change when she used a bill to pay for gas, right? (remember most facilities have cameras)
RIGHT??
If she's got no valid other excuse and can't successfully spin it otherwise, she'll need to shut & lawyer up ASAP like M9 said.