I'm pretty sure i saw the exact same sentence but without the 'mi' later on. Other times i added 'mi' before 'ges i' and it was marked wrong. I'm not sure when to add it and when to leave it off, it's not clear to me...
It should be accepted for every sentence for the future, past and conditional.
these all mean the same thing,
Mi fydd hi= Bydd hi= she will. If you get an answer like that marked wrong then I'd recommend reporting.