For easiness, there can be no easier class to play than pyro powertech/Assault Specialist Vanguard. press 4-5 buttons to kill stuff. I'm not saying you will play it well, but it is doable. to play it well, you need more buttons:
basic pyro rotation: TSO - IM - TD- RS - FB - RS (If PPA Procs) (the 5 buttons I was talking about), if she picks republic, find the abilities that mirror these.
the Acronyms list, if you dont know the abilities by heart can be found here: http://www.swtor.com/community/showthread.php?t=431883
for PvE, use this spec: http://www.torhead.com/skill-calc#301hMbZ0cZfhrbzGhrs.2
or the vanguard spec that's like this one.
Oh and, if she's not into the whole dark side thing, boounty hunter is a good class to play as Mako likes light side choices.