i know there are different ones for different ages, but I am not comfortable with my daughter able to roam the ship alone. I'm surprised this is allowed as it isn't safe. Can she go into the younger group where she will have more fun? She is very small for her age and close anyway to that age range, plus has special needs. Otherwise she won't be able to participate. Do they make exceptions?
As others have indicated, the upper-age-limits of the kids' spaces are hard limits.
DCL will not adjust those. If she is 12 or younger, she is welcome to attend the Oceaneer Club/Lab (ages 3-12). You can restrict her ability to self-check-out if you so choose, meaning she cannot leave the Club/Lab until an adult in your party is present to check her out. If she is in the overlap age of 11-12, she has choice of Club/Lab or Edge.
Once she is at Edge (ages 11-14) there is no check-out and she will be "free" to move about the ship. However, many families of young tweens find they can work out a system of family rules that keep both parents and child happy. Some rules might be:
child must text/call parent when leaving Edge;
if not going to meet up with a parent, the child must return directly to the stateroom, alone
no friends allowed in the stateroom
not allowed to go to anyone else's stateroom
You mention your child has special needs and "won't be able to participate" -- do you mind explaining a bit more? She will need to be able to function in a group environment, as DCL doesn't not provide or allow for direct 1:1 assistance even for disabilities. Generally if she is able to attend school and at least part of her time in a regular classroom, she will probably be fine at the Club/Lab. If she is at least 13 yrs old, she cannot attend "secured programming" (drop-off childcare) at the Club/Lab but you can take her there during "Open House" times which are generally scheduled for at least one hour per day at each kids' space. You may need to stay with her if necessary.
Enjoy your cruise!