How to switch from a text message back to iMessage?

[iMore Question]

How to switch from a text message back to imessage

For my sister-in-law's vacation, she went to mexico. She and I iMessage lots. When she left the country, I couldn't reach her via iMessage (blue bubbles). Only by Text (green bubbles). How do I switch back from the text (green bubbles) to iMessage (blue bubbles) now that she is back in the country?
Thanks

 

[Just_Me_D]

Re: How to switch from a text message back to imessage

You shouldn't have to do anything, especially if iMessage is enabled on both devices. If anything, the both of you can try rebooting your iPhones.