She was skint, getting final demands for bills (not sure why as she was subletting from Evelyn and all the bills would have been in her name)... Bethany let her believe she'd get paid loads of money for selling her story, then it turned out it would only be about £30 so she changed her mind. Still skint, she then went through Bethanys bag when the opportunity presented itself and nicked a fiver.
Lauren apparently left her Mums when her Mum got a new boyfriend and preferred him over her, back when Lauren showed up homeless and was kipping in the salon. Thats when the impression was given that Laurens Mum was a rather brash, loud, money money flashy boyfriends kind of person. She really hasn't been mentioned until now so I guess we're all supposed to have forgotten that!