Frustration
I don't know about the legalities of all visas. I do know when my American ex-sister-in-law (living here with my brother, US/EU citizen) got divorced her visa-by-marriage expired right away. But that's not the point in the case of BA -- and I am not defending them -- I think they have such a huge workforce it has to be a blanket policy.
My recommendation (and I know you haven't asked for it) is to leave BA alone now until 6 months or whatever it is have gone by - and focus on the others who are recruiting here. And not just for fixed term or seasonal periods either. Previous flying experience is not necessarily the lynchpin to getting in some place else when the season or contract is over so someone leaving BA at the end of their 11 months is not guaranteed to be snapped up by another airline.
Once you are in the business it's hard to quit, and if you loved it it would be almost as devastating not to get your contract renewed as it is to be rejected at the start.
I'm not much help but like I said, tell her to get back on the horse.
90.