[Cola]

I'm not a Softbank/legacy Vodaphone user, so I can't say for certain, but as far as I know you should be able to send and receive PC email account-based messages. That's the way it is with DoCoMo now and the way it was when I was using Au a few years ago. Why not just do a quick experiment and send her an email using whatever email service you normally use on your computer and have her send a message to the same address?