Congratulations on the adoption!!!! My kids are adopted. Have you known the child long? I wouldn't do this trip. This is prime opportunity for meltdowns and overwhelming her before she trusts you. Cocooning even an older teen is a good idea. At least you'll cocoon her with your presence even if you can't get out of the trip! I wouldn't give her spending money. I too would encourage her to ask. Or offer her choices-which of these do you like better? Would you like to get it? Lots of choices the whole trip. My life is two choices! Our teacher pointed to two seats for an adult walking in late-do you want to sit here or there? Haha! It will become ingrained in you! In my trauma class they also taught us to play games with m&m's. Choose one and tell us what feeling the color represents. Everyone in the family does this while relaxing. Feelings is just one idea. It's kind of like an ice breaker. Another one to help them learn to trust and ask is make them ask for an m&M. DOn't hand them the bowl until they ask. The teacher found her child "stealing" candy. Because they thought if they asked they'd get told no. Try to make lots of gentle eye contact, and lots of touch. LIke a nb needs kangaroo care--but always ask before touching. Can I give you a hug? Can I touch your shoulder? Let's go this way. Let me see those beautiful eyes. Now, do you think we should have Mexican food or French market? Let me see those brown eyes, Now. How are we feeling? DO we need a break? Holding hands as a group in the park could be a fun way to integrate touch, build trust and help her feel safe in a new, loud, visually stimulating place.
Take lots of breaks. Bathroom, water, food every 2 hours. Set a timer. It can be some snacks you bring, make sure there is some protein every two hours. (nuts are good if no allergies) A lot of kids from hard places simply can't tell if they need to do these basic body functions, even at what we might think of as an older age. It's OK to think developmentally maybe she's 8 or 10 or 12--there have been real changes in her brain chemistry and wiring from all she's been through.
If she is having hard time standing in line or is dysregulated because of all the overload of sensory input you can ask at City Hall or one of the green tents for a
DAS. That way you can wait for your rides in a restaurant, or quieter area of the park where she won't be touched. My oldest is super sensitive to touch and can't handle being in lines.
White noise for the hotel room may be nice. We use an app called white noise baby. You can put it on phone or ipad.
She may have never been on a plane. Describe in detail what the steps to traveling are. It may be nice to make a visual to check off. So if she's afraid of asking she can refer to it so she knows what's happening next. You may want a similar visual schedule for Disney. Plan out your first two rides of the day and alternatives in case they are not open yet. OUr kids need super predictable schedules to start off the day. We list out our preferred morning rides, and where we'll have lunch. Also a few rides we could do as alternates.
Also, riding in a car, a certain color, being in a bathroom. These are all things that might trigger something from her past no one has told you about. In one case I heard of the girls job was putting the trash out. THey started finding trash all over the house. Turns out the kid was hiding it before the trash got full so they didn't have to take it out. THey had been abused behind a dumpster.
Sorry I"m all over the place and probably writing more than you want to read or some things you've already considered.
She will get a better idea of what she wants to do. One of my 15-year-old's biggest DCA priorities last fall was meeting Spiderman and Captain America 
. If she's into a particular character, or music or drama, or shopping, that will guide some of your choices. 
