Hi Susana28,
Do you have a link or perhaps a picture you can provide? Where did you hear her name? I tried Googling her name and the only thing I could come up with (in English) was a quote from "a 23-year-old engineering student" with the same name regarding Berlusconi, with no mention of Guillaume.
Great Seducer Silvio Berlusconi woos Italy again but this time he's got company - Times Online