I don't know about Orange, I'm with 02, and the answer for me is YES. However, it's a great deal cheaper than phoning... my OH works in Europe a lot and we rely on text to keep us in contact.
You'll need to make sure that the phone going abroad is set up for international roaming before she leaves the UK.
You should find the detail you need on the Orange website
http://www2.orange.co...e?pagename=PersonalIR
Looks like the costs depend on which calling plans are being used.