How to restore to Leopard/Snow Leopard from Lion without any disk?
There are two possible solutions from my limited knowledge:
First method
Install the OS X Recovery Disc Assistant on a USB drive and reinstall Lion.
From the OS X Recovery Disc Assistant guide:

To create an external OS X Recovery, download the OS X Recovery Disk Assistant application. Insert an external drive, launch the OS X  Recovery Disk Assistant,  select the drive where you would like to install, and follow the on screen instructions.
When the OS X Recovery Disk Assistant completes, the new partition will not be visible in the Finder or Disk Utility. To access OS X Recovery, reboot the computer while holding the Option key. Select Recovery HD from the Startup Manager.

If her Recovery partition won't let you install already, I'm guessing there's a chance this might fail, but it's a least free to test and see.
Second method
Buy OSX Lion from Apple.
OS X Lion is still sold by Apple, so you could just buy a new disc and install using it.