looks like you have already been researching it based on your other posts..
The best thing is to make sure her immune system is strong and that she is as healthy as possible. There are a variety of preventative measures, like taking the amino L-Lysine, which you will find if you search around this forum.
The reality though, is that there are no absolutes. If she has had it for a short time, there is usually a greater chance of more frequent outbreaks as the body has not built up enough strength/antibodies against it.
For me, L-Lysine, regular exercise, avoiding acidic foods, coffee and alcohol, and eating well has made outbreaks very infrequent.
There are also a variety of products which people claim have helped eliminate outbreaks entirely, like "Cellfood" which apparently oxygenates the cells inside the body, but it is important to remember that everyone reacts differnetly to all of these products.. Some have great sucess and some have none.
The bottom line, unfortunately, is that there is always a risk..