If she's being genuine, she says she's in the UK studying (or could be late 20's earning some money, whatever). If you take her at her word, showing her face would fuck her over; everybody at uni would know, family would find out, etc.
I could be wrong but think she hides her face because she genuinely needs to keep doing this without people knowing what she does.
Of course, if she plugs a PPV saying she'll show her face for more money, then I'll take back what I said.