Two STEM people I know who did Oxbridge took the "self-taught coding and moved into tech start-up" route.
One was ND and couldn't have managed the big company vibe.
One tried other graduate careers, but ended up at a start-up as that smaller environment suited better.
I think they needed to pass a coding test for this, and got on with the start-up team. No-one cared about degree class.
Two blokes I know of who got Thirds (relatively recently).
Both had a few years happily pottering about in customer service then ended up doing Data analysis and climbing the ladder, moving company for better salaries etc.
All progressed fine, homeowners etc.
Usual rule of once your face is in the door, it's easier to move around.
With one guy, he wanted to get back on the graduate career path/thought about trying to requalify...but of course financially just getting on with it worked a lot better!
There probably is a current version of coding or data analysis that would be useful to learn.
It might be better to stabilise, get the degree, stay at home, quietly upskill for free, build a portfolio, see if she can get work experience with the right kind of company.
rather than think and worry about paying out for additional Masters degrees (which is more academic pressure).
A lot of Masters degrees are simply cash-cows for universities and won't necessarily make the crucial difference in applications.
(A very common experience of people who have done paid post-grad courses -
...is to realise that they could have done the exact same job without the Masters).