Yeah, that's my option, i can do the same with any payg simcard. It's just the hassle of the few days delay to transfer it to that and then another few days to transfer it back again. She uses her phone for work so it's a reasonable amount of downtime whilst her number is in imbo.
The only other option seems to be ID Mobile, but they use the Three network which is garbage at our house.
Might just buy the phone and stick with her current sim only deal, was avoiding that as it seemed to be more expensive annoyingly!
Transferring your number is much easier nowadays. You can text to get your pac now so you don't have to waste time talking to the cancellations department and it transfers next working day. It is a hassle transferring off a network just to get back on it, so depends how good the deal is.