She will need to get Blackberry services from her new carrier in Spain but it shouldn't change her Blackberry ID and BBM account. Same phone, same software, same ID. Since that runs off of the data line...
The BIS ordeal is different as far as I know, it is how you receive email and that might be affected.
To check it out, I switched sim cards between my two BB phones (same carrier, personal line and company line) and had a go. I can use my e-mails as well as BBM and my Blackberry data services but keep in mind this is the same carrier.