After being stuck in Barcelona without an international cell phone (very long story), we purchased an international phone from
http://www.mobal.com/ . They sell two versions, one for $49 and another for $99. The difference is the number of countries in which they will work.
Essentially, you pay for the phone and then there are no other fee's unless you use the phone. There is a per minute fee that varies from country to country.
At the time we purchased the phone, it was cost prohibitive to to buy a phone that would accept an international sims card and pay international calling fee's. Things have since changed and the latest blackberry phone my wife has already has a sims card for international calls. I haven't looked into it but I think it's probably going to be less expensive for use to use her new Blackberry Storm than the phone we purchased from Mobal but, we'll take both phones when we are out of the country anyway.
The one time we needed the Mobal phone was in Ireland. It worked very well and was, IMO, cost effective compared to the options at the time. If this is a one time need and you daughter isn't going to spend hours on the phone during her stay, the Mobal phone may be a cost effective option for you. You'll have to check out the per minute prices on their website and check out the options offered by your current cell phone provider to determine which is the most cost effective and easiest to use for your needs.