I'm basing what I'm about to say on what we were told by our mortgage broker when we bought our house 3 years ago. If I get anything wrong, I'm happy to be corrected.
When a mortgage company is deciding whether to grant you a mortgage or not, they look at a lot of things. It's not as simple as "I pay £500 a month on rent now, so I can afford £500 a month on a mortgage." They want to know their investment is safe. Can you pay the necessary bills? Can you maintain a good state of repair? Some mortgage companies insist on home insurance, life insurance, mortgage protection, can you afford those? Will you still be able to afford all this in 5, 10, 15 years time?
They go through your bank statements with a fine tooth comb. What did you spend that amount on? What did you buy on this day? How often do you pay for that?
They look into your employment history. What was this job? Why did you leave? Why have you had x number of jobs in the past few years? Have you ever been dismissed? Why?
They want to know your future plans. More kids? Marriage? Change of career?
Can she genuinely answer all of these questions honestly, and prove it all when asked? I can't see a mortgage company wanting to gamble money on someone who worked 3 shifts as a nurse 6 months ago, has admitted on several occasions to using her overdraft to pay for holidays and expensive hotel stays, and orders take aways 6 nights out of 7.
I'd put money on her claiming some kind of discrimination when they turn her down.
It's her go-to answer when she doesn't get her own way with anything.