Louisville Slugger - Coach's Tips
Go to this website and look at the chart on the bottom. Looks like they would recommend a 32" length, but 1" either way isn't a huge deal.
As far as weight, go somewhere that sells bats and has someone there who can work with your daughter, it's not that hard to tell when the bat gets too heavy they can't control it or swing properly, just try different weights and once you get too heavy for her back off an ounce. From your description I would guess she's in the 20-22 oz range. I'd be real hesitant to have an 11 yr old swing a bat any heavier than that. If you're unsure err on the side of a lighter bat.
I'm pretty brand neutral. Find a bat in your price range that she likes the color of and go with that. You can worry about getting her a composite bat when she's older and has a legitimate chance to improve from warning track power to over the fence power. It's a common phrase among coaches in fastpitch that there are plenty of kids out there with $400 bats and $.05 swings.