Easy method is to goto market.android.com (on a pc, not a phone) and login. Her apps will be there, just select download and they will automatically dl.
For the record anything you've bought is safe - you just need to remember what you've bought, goto it again and it will offer you the download button rather than the pay button.
The reason you're not seeing them again is possibly because it thinks the phone is a new device and then google play does something...odd. you only get 1 shot to re-download your standard apps when you login to play after a format and if you don't download them all for whatever reason then play doesn't offer them again. I go through about 18 Androids a year, for the ones I have market access on i've just learned to use the full browser for push download to be honest