A couple of options but my first question would be is she a certified jr. diver? If not, I don't think any of these places will allow her to dive. You could find someone to take her on a Discover Dive if she's 10 by then:
To take Discover Scuba Diving, you must be:
At least 10 years old
I don't know much about PADI and kids programs but that's my impression.
Sunset House has a saltwater pool used for training and access to the reef. It's really shallow but since it's open to the ocean on one side there is some interaction with the fish/reef. Jumping off the end of the pool/dock it's 12'.
They do a resort/Discover dive but it's $100 - yikes...
Some of Eden Rock downtown is really shallow.
The coral reefs rise in vertical cliff faces from a 40 foot sand bottom to within a few feet from the surface.
There's stairs right into the water so it's really easy entry. I've seen smaller kids there with their parents. And they do a Discover Dive program which must be done offshore there as there's no pool nearby.
Go when there's no cruise ships in town though. Or late in the afternoon when they're about to sail. Otherwise that whole area is a zoo.
A more advanced option might be Stingray City. The hard sand bottom there is 14-15'. But she might be a little intimdated by the size/strength of the rays brushing up against her. And it can get a little cloudy if everyone can't stay on the bottom and kicks up the sand. The trick is to slightly overweight and use your BC to move vertically - not your fins.
If she's fearless, it's really a blast - they advertise it as the most fun dive in 15' on Cayman. It's a boat dive so she'll have to GS. She'd also be able to snorkel above you there and swim down. We had several families on our boat with young kids and that's what they did. I'm not sure anyone will do it as a Discover Dive though.
I think Cemetary Beach might be a bit much for her. Getting in/out of the surf line can be a bit tough. Unless you tow her gear out and help her don it. It's about a 100 yd. swim out to the reef - although it is really shallow once you get there.
Does she dive with an 80'? Finding a 63 might be hard to do, almost all of the diveops/resorts won't let you remove tanks from their premises. There is a rental shop in West Bay that is fairly close to CB.