Shes getting a AR for Christmas

[challenger]

Having owned an AR pistol for a few years, I can assure you that the novelty wore off very quickly. I would suggest to go the rifle route and let her customize it.

[Junkie]

If she's willing to go through the hassle of SBR I'd do that. Otherwise I'd go rifle.

For people with less upper body strength (women tend to be in this group), I'd recommend a 16" midlength lightweight or pencil barrel with a lightweight handguard and a comp/brake. Something like a BCM ELW upper with KMR or KMR Alpha handguard, although I'd probably swap the muzzle device for something that's intended more as a comp/brake than a flash hider. Yes, it's obnoxious... but a lightweight AR has more recoil and I'm assuming we're talking about someone without much upper body strength.