I'm an NQT at the moment, and there are definitely positives to teaching. It might not be her career for life, but that's ok, and she will always have QTS once she gets it.
There is a big tax free bursary for languages now (£28k I think). I got £26k for training in biology and easily saved £10k for that. If she's able to save a decent chunk of the bursary, it could be her house deposit.
The pay isn't bad, even early on, if you live in a cheaper area of the country, and for the first 6 years it is very likely to go up every year. When she qualifies, there would also be retention payments for language, which will boost her pay. I live in a lovely area of the country, and even early in my career, my pay is good for the region. Teachers are needed everywhere, so she can pretty much choose where she lives. If she's willing to live in certain areas, I believe MFL teachers can qualify for a SF forgiveness scheme as well.
Even early on, I can really see that different schools have different cultures, so it's all about finding one that suits you, as well. As a language teacher, it's likely she'll find it relatively easy to get a job!
However, there are a few things I would mention:
-Most unis expect MFL teachers to be able to offer two languages, usually a combination of French, Spanish and German. If she's only done French to GCSE, she might be asked to do an SKE before she can start her course- there is a bursary for this, but it would be hard to do alongside the third year of her degree.
-I would say the people who came through the school-uni-PGCE route on my PGCE struggled the most, and a quite few dropped out. If teaching is the long term goal, it might be a good idea to take a year out between her degree and the PGCE- get a "real" job, get used to how work works, maybe spend some time living in Spain or another country to really immerse herself in the language.
The PGCE is really hard work, and I think it's even harder doing it if you have no real experience of a professional job, as you're also trying to learn professional norms on top of everything else!