"£100 or so" does not buy a decent bike new, sale or not. It will buy a bike which goes, but where the components are made of cheese and don't work very well, it dissolves at the first sign of rain and when it goes for its first service it will cost far more than the bike is worth, so she'll be best advised to scrap it. Landfill, in other words.
She could get a reasonable bike for £100 secondhand, but she'd need expert help.