I'd have a quick read through [url=http://finalfantasy.wikia.com/wiki/Junction_System]this[/url] and [url=http://finalfantasy.wikia.com/wiki/Guardian_Force]this[/url] if you've never played before; it should give you a good understanding of how things work.
If she's with the Garden group, she will have been a student there, transferred to Balamb for her final test. And she'll need to run like hell to catch the airships afore they take off >>;
GF is good, ninja is... alright so long as she isn't stereotypical ninja (i.e. black pyjamas and hand signals). But overall, yeah no problem.