to governemt site is not all that clear on whether you have to be resident in the uk after you apply, however, they will need to contact her at some point over the six odd months it takes, plus she'll have to go for an interview and so on, and that's going to be hard if you don't have a uk address. i would also imagine she'll have to send her passport off - not great if you want to move abroad!, plus even if she does apply, there will be at least six monhs before she'll have any cover. Travel insurance?