She's going to Portugal?
She will meet some nice Portuguese boy, and she doesn't need you calling in the middle of him making goo-goo eyes at her
She needs to make sure her BB is unlocked for use on other carriers, and when she gets there to purchase a local GSM SIM card for a local carrier, and SHE calls you from it. (I think would be the cheapest way). How do I unlock my BlackBerry? - BlackBerryFAQ
But on the 8700, you can't turn off the data, and use the phone only, she she still might incur some outrageous data charges.
Does someone else recall what is a good idea for the data?