Well she could listen to a lot of uninformed tosh here or she could do the following: (any reference to them gets binned.)
Doing her exams before she goes is not always necessary (I didn't) and it will bump up the costs, however, it will also make her time in Florida much less stressfull.
Re flying in the UK afterwards - it should take around 2-4 hours to get checked out on a UK club afterwards. Beware any club/instructor who tells her different, that will be due to a combination of their ignorance and greed.