Jet- I understood it exactly the way "wmferg" has described it. I would also like to add that I understand that the 90 day period starts the day her visa is accepted.
I do not want to 'rain on anybody's parade',
but:
Problems do not just go away. If there are problems before the wedding, the same problems will still be there after the wedding (e.g. mother-in-law).
I don't pretend to be able to foresee the future.
However...
My own experience - poor as it is - tells me that if there is a suspicion of a problem, it is a good idea to get it 'talked through' - early.
(I have learnt that because I did not follow that advice myself!)