You're correct: if she can send e-mail, then she has (some) internet connectivity which also suggests that she has Data Roaming turned on (though you might want to have her check that).
Could be reception. I can't see it being Voda limiting what she can access. Might be something to do with the proxy: have her check what it has under APNs (Settings .. Mobile networks .. Access Point Names) .. I guess it should be something with an ie on the end.
