ChrisLei...
I thought I'd put my response to you in a separate post, b/c I figured any other moms and daughters out there reading and wanting to bring a doll to the world might like to read it too.
AG dolls are a ton of fun at Disney World (especially in the hotel rooms b/c the maids always make cute displays with them!) I was 8 the first time I brought an AG doll (Felicity) to WDW. My mom did set down some rules, though: Felicity had a special little backpack that she fit into completely. Unless we were in the hotel room, Felicity had to be in that backpack at all times.
I did get to choose ONE and only one day to bring her into a park. But I wasn't allowed to bring any doll accessories (jewelry, play food, even shoes!) and I could only bring two extra outfits (and they had to be simple outfits too...as in just a dress instead of some outfit w/ a belt, skirt, shirt, jacket, etc.!). It's amazing how easy it is to lose just one piece of those little accessories or just one shoe!
Felicity made it home safe and sound, and I still follow most of my mom's rules. (like Epcot was the only park I took Nicki into!) I think your DD would have a really fun time with Marisol at WDW, as long as you set down some rules like my mom did to keep Marisol and her clothes safe.
A few suggestions I might make that my mom didn't: put Marisol's hair up in a bun and leave it there for the whole trip! I had Nicki's hair in a ponytail most of the time, and the one time I took it down (at Epcot) I regretted it b/c it tangled so easily! Also, I'd advise bringing a plastic bag along, like the Old Navy bag I brought, for your DD to carry Marisol in if & when she takes her into a park. That way, when she gets tired of carrying Marisol, she'll put her in the bag and then put it somewhere safe, like under the stroller, instead of on some random shelf!

(at the kidcot stops, or when we went on a ride, I would put Nicki in her bag and keep it around my wrist so there was NO chance of me leaving her!)
And of course, there's the old trick of writing your name & address on the back of her (or on a sticker on her back) and then if you DO somehow lose her, a CM would hopefully find her and send her home! (Just a funny side story: we took the wrong stroller at Disney World (it looked exactly like ours and had nothing on it) and we didn't realize until months after we got home, when Disney sent us our REAL stroller. At first we had no idea why they were sending it, and then we saw Mom had put an address label on the bottom!)
I'm sure you (and anybody else out there reading) have already thought of most of this and know most of this, but I thought I'd just throw my experiences out there in case they help!