For a start, she will need to have a Bachelors degree in a subject strongly related to the national curriculum. She will also need Maths, English and Science at GCSE, and it will help her to have A levels too. They may or may not consider her Masters. But then I'm sure she knows that.
When I originally applied for my PGCE, I was turned down by three universities. At the third one, I asked why, and was told that 'other candidates were stronger in Maths and English'. This despite my having very good GCSE passes at a time when they weren't compulsory for mature students and a 2.1 Bachelors in my subject. Since I got into my Bachelors course via an access course, my university tutor says their reasoning was probably born of the fact that I didn't have A levels in maths and english. Between-the-lines shorthand for 'we don't want mature candidates'.
Always persevere, because it can pay dividends, but I've known quite a few people who applied to teach as mature entrants and who were turned down before the interview stage. Many of these have been obvious, natural choices as teachers - born to it, almost. Yet when I look at the standard of some of those who do teach ... !!
It does very much seem that universities want candidates whom they can mould into the ways of the system and with not too much in the way of experience, which would make them able to question what they're fed.
My PGCE eventually came from a former polytechnic, with a very open attitude. Could be worth a try. Also, has she tried the Open University? Not sure what OU's nationality requirements are but again, as their name suggests, they're a lot more open as to who they accept.