A lot of the divesites in the BVI's start in the 20-30' range.
Some around the Dogs or Cooper Island don't exceed much over 40-50' ever. One of the better dives - The Chimney off Great Dog Island never exceeds 45'. Thumb Rock off Cooper is 60' to the bottom but the top is 15' below the surface. I spent the better part of that dive at about 20-30'. Cistern Point in the same area starts at 20' and goes to 40' max. Aquarium off Virgin Gorda's Yacht Harbor is another really shallow (35') excellent site. And the Baths nearby are a great snorkel site. She could even dive the shallow part of Seal Dog, the day I was there, there were thousands of Silversides no deeper than the 1st 20' or so. There was a Barracuda and a couple other fish hitting them nearby though. At a site off Ginger Island - can't recall which one - we did a shallow dive near some rock ledges - a couple of snorkelers from a catamaran nearby swam down to join us for part of it.
DiveBVI lists depths on their website. They run an excellent operation also.
Dive Sites | Dive BVI
Another option might be Curacao. The Tugboat - famous dive site on Curacao - is 20' deep. There's also a pier nearby that starts at - 0' deep...lol.
Parts of Varsenbaai are shallow as well - but the wreck is deeper - close to 80'. We found seahorses at the mooring at 40'. And turtles in 6' of water just offshore. The facility mgr. said they're always there.
Nos Kas (Habitat's reef) also has a shallow area. I burned a 2nd tank waiting for my friends filming flounder and tropicals in the shallows inside of where they moor their boats offshore in the afternoon - it couldn't have been deeper than about 20-25'. The reef there rolls off at about 40' also. So she could do part of it.
The first reef at Porto Mari nearby starts at 6M - 18' also. The second is considerably deeper...
Since Sunset Waters closed/was demolished recently I don't know the status of the dive there now, but when we did it, there was a protected breakwater with an opening through it that led to their "plane" wreck (Cessna). It was at 40' max. It's likely still there, whether you can get to the beach via the road is another question.
Theoretically she could also do the Dolphin Dive at the Seaquarium - not sure if there's an age requirement. My log shows it at 50' max. And I all but sat on the bottom.
For a new diver, I'd pick Curacao over Bonaire unless you only plan to dive off the resort docks. Bonaire shore entries are a lot rougher, most are over ironshore, submerged ironshore and/or coral rubble. It's sharp and slippery. Maybe not the best idea for a 10 yr. old balancing a tank - even a 63' on her back. I have a 4" x 1" scar on my shin from stepping in a hole at Angel City - there was a sharp coral at the bottom of it. After that we mostly dove the resort docks or found easy entry points through the ironshore. But some of those were near more advanced divesites further south - currents could make those very difficult for a 10 year old. Not that diving the resorts is a bad thing - almost every one is on a named dive site.
Bari Reef was another shallow dive, we spent 1/2 the dive looking for fish in the shallows. There's rubble from an old pier there in about 10-15' of water and the mooring was about 35'. One option she may like there is that you can do an official REEF fishcount with a naturalist at Bonaire Dive/Adventure - your results get reviewed and submitted by them.
