Find out which carrier in Italy uses the 1800 MHz GSM standard and she'll have to buy a SIM from that company when she is there.
Not sure if any or all of the italian companies use that frequency, some may use the 900MHz GSM frequency (which the Nokia 5200 cannot use).
Either way she will not be able to use her SpeakOut service or SpeakOut SIM card while she is there.
Europe uses 900 and 1800 bands. The Nokia 5200 only supports 1800. That may be sufficient depending on your carrier's coverage. You will also need a SIM, either an Italian one or an International one. See http://www.prepaidgsm.net/en/italy.html for available SIMs, prices, coverage, etc.
There may also be additional bureaucracy for a non-resident to buy a SIM (IIRC Italy requires a national ID to buy a SIM.) You may want to check with the folks on prepaidgsm.net's forum.