First off, congratulations to her, that's a fair old achievment.
Secondly, bikes. The ones that always get mentioned time and again and we've had one too are
Islabikes. They can be equipped with rack and panniers from the off. That said, you can tour on nearly any bike, especially if you've already done so on a
Halfords kids bike.
We've just completed a taster tour in Scotland with the kids. Far more modest than your 215 miles but my two had a Ridgeback MX24 and a Scott Voltage jump bike. I neded to make a few changes to both but we got rack and panniers on them and the kids carried their own stuff and they worked beautifully for touring. There's a write up in my blog and the relevant bit about what I needed to do to the bikes is at the end.
I mention it because the Islabikes are good but expensive. If she isn't tall enough for a 24" yet, then they may be the only option as below 24" frames are etiher a funny shape or a bit too small for a normal rack. With Isla, I had a 20" wheel bike with rack and mudguards and it was very light. Not that we ever toured on that one but we could have.
