You can't replay a script back on an iPad (iPads don't allow apps to import custom files, and it would be a very complicated, memory intensive process anyway), you will need a computer to actually create a video recording. There is no way round this.
Scripts are a set of instructions for ArtRage, telling it to 'move this brush there, zoom in this much, change that colour'. You will need one of the desktop versions (ArtRage 3, Lite or 4) to actually use that script. When ArtRage is following the script, you can use screen recording software as described to record the painting process, just as if you were painting live on the computer.
Quicktime on Macs can be set to record whatever you're doing on your iPad screen, allowing you to ignore scripts entirely, but you will still need to be hooked up to a computer:
http://ioshacker.com/how-to/use-quic...-running-ios-8
[Edit: forgot you were on a Mac, you can ignore this recommendation!] - For a decent free program on Windows, there's
https://screencast-o-matic.com/home - the main limitation of the free version is that it can only record 15min at a time.
Your friend CAN use the ArtRage 4 demo to play scripts back -
www.artrage.com/demos - so if she knows more about this stuff, you might want to leave that step to her.