My girlfriend is about to go abroad for a couple of weeks. She will not be enabling roaming on her iPhone 5 (running iOS 7), and instead rely on wifi through her trip. The last time she went abroad, she was unable to talk to me via iMessage but said she could receive my texts. What settings should be tweaked on her or my end so we can iMessage even when she's abroad? I have iMessage active on an iPad 4 and an iPhone 4S, both on iOS 6.