There are some plus points for doing flight training in Florida but some/many minus points as well.
Obviously the cost can be a lot less but make sure there is enough capacity, both instructors and aircraft, to get the hours required. One word of warning, doing intensive flight training is very tiring and may not be as productive as doing training over a much longer period. Your friend should have a backup plan just in case she does not achieve the PPL in the time she has allowed.
The weather over there is what most people go for. In my experience the weather CAN be as unpredictable as over in the UK. Very low cloud and thunderstorms can last all day and strong winds and turbulance can pick up very quickly. It isn't always as it looks in the brochures, a lot depends on the time of the year (avoid the hurricane season!).
Navigation, RT and procedures are the big down sides. As you have probably heard they are a lot different in the USA, not neccessary better or worse, just different. After returning to the UK there is a lot more adapting to be done, something which a pilot with a freshly earnt PPL could do without.
What about taking her Practical RT exam? I have heard that many schools don't have the facility for these to be taken in the USA.
The quality of schools can vary widely, try and pick one using recommendations.
Getting a visa is not as straight forward as you may think. The school will provide the sponsor form, they may charge for courier delivery though. The application forms can be dowloaded off the internet, and are also available at the Embassy. Make sure the pictures taken are the right size (they are a different size to UK/European passpord pictures!) and have the right color background - very important! Make sure the paperwork is 100% correct, take time filling out the forms. Be prepared for a long queue and wait at the US Embassy.
I could go on but I'm sure others will add their views ....
Skyhawk-N.