True but in that 6 months she's had time off for Gran Canaria, Mexico, Las Vegas, Santorini and she's planning NYC as well. That's at least 4.5-5 weeks of no pay.
She also hasn't been working all day every day (or even 9-5 Mon-Fri) for that entire 6 months.
Her in-laws paid for a crap tonne of stuff for them, including holidays, so she isn't making as much as she wants to make out - surely if you were making £600 a day, 5 days a week for 6 months - over £60,000 before tax and NI, you wouldn't be desperate for freebies/relying on parents in laws to fund you/shopping at Primark constantly?