My vote is lessons... But the teacher needs to teach music your daughter is into.
My problem was that after getting into Rock, the classical pieces I was playing were just technical exercises, but I wanted to play something people *knew*.
I switched teachers, but to someone that taught me scales. Wow, I hated that, so I quit lessons. Now I wish I hadn't... I can't write a solo to save my life, but I can learn and play most everything (depending on how much time I have).
Tabs are nice and easy, but note reading is a skill I'm very glad I learned, but you might argue is out dated...
I'd suggest teaching musical theory once she is having fun with the Guitar... but make it practical... I know (well, used to know) a lot of theory, but I never applied it practically, so when it comes to jamming with friends, etc, I have to memorize and adapt, as opposed to know what's happening, or going to happen.
I guess, a lot depends on the type of music she wants to play.