(OK, as a female player who plays all the combat roles, I gotta jump into this one.)
I ask you to let her try some options for herself! Make your first low-level character with her (say, until you guys get your ships) so she gets used to the UI and general combat mechanics, and then let her make a few of her own. (You can always play your existing characters while she does this.)
The choice for a main should be up to HER. Being "attached" to one's character is a big component of games like this, and from my experience, females are more likely to identify with/feel attached to theirs and use it as a motivation to keep playing. If she sees her class and faction as her own decision, it will greatly help the attachment process, and mean she would be more likely to stick with this long term.
Also, not to be blunt, but unless she's mentally challenged, she should be able to handle ANY class and spec just fine! The leveling process allows PLENTY of time for this. It's easy enough to get by, and maximizing more complicated classes is only really relevant in endgame, anyway. She's got you to give her tips, after all. And getting her up to speed would be even easier if you guys play in the same room.
The only time someone of average intelligence shouldn't roll a more complicated class, is if they don't have anyone like guildmates or real life friends/relatives to give them advice, and are unaware of the resources on the web.
I also second the advice to suggest a tanking or dps class first, as it will make healing easier if she decides to go that route.
installed swtor to my gf... she's making a jugg. male , uber ugly... she said
'it's to match all those girl chars you made'