Wear bug repellent especially in the evenings. Get the strongest stuff they have. Also, ensure there are not open spaces in the room she is staying to the outside where mosquitoes can get in. A few places we stayed at we had them come in and got the hotel personnel to come and spray the room down with bug repellent as there were already mosquitos in there.
Another control is to buy a mosquito net while there. She can drape it over the bed to also keep bugs off.
I know a lot of people who have gone for many years without any issues. My wife was with me and got bitten, but she is totally fine. I was just unlucky.
I hope she has a great time!!! Lots of awesome places to go there and the food is amazing.