Curacao will prove to be better than Bonaire for a teen.
The diving is the same, low current, lots of coral, lots of fish. A big difference is that most of the beaches are also dive sites with onsite facilities
NONE are on Bonaire and many entries are rough and require picking your way over ironshore and coral rubble both on shore and in the water. It's razor sharp and collects urchins which live in the holes you step in.
Honestly the diving is so similar that I told my friends once on the surface at Sunset Waters (Cueacao) - "congratulations, you've just seen Bonaire"
It's easier/cheaper to get to. There's a whole lot more for a 14 yr old to do in town and if the farther from town, the quieter it gets - noticeably quickly. Many hotels also offer dive packages but unlike Bonaire there's only 3-4 dedicated dive resorts.
It's actually more green on Curacao also, Bonaire really is a desert island - mostly scrub, cactus everywhere. Around Christoffel Park mid-Curacao its actually a forest with big trees - and hiking.
More/better shopping, Nightlife if you can leave her. Even some of the local fast food chains like McD's on Curacao. We eat at a Denny's in Piscadera Bay b4 shore diving nearby.
The diving is just better. A lot of South Bonaire is the same - it's the same reef 500 yds. away.
The Tugboat is a signature Curacao dive - it's 17' deep. The pier next to it is 40' Arguably ome of the best dives west is Playa Kalki, maybe 60' max and a lot to see in 30'. Nice facility at Go West - lockers, clean, a dive dock that takes you 50' closer to the reef.
Really
Great Parents would pop for the Dolphin Dive - it's done in shallow water off Lions Dive/Ocean Encounters. Almost an hour w/3 dolphins who seem to like it as much as the divers. $200pp.
If I'm currently showing it - one of my avatars is from there.
www.curacao.com has everything you need to know
Willemstad is the reiongal port so there's more activity there. the famous Swinging Bridge betweeen the 2 downtown areas. Ostrich Farm, Sea Aquarium, beach clubs, casinos for the adults and good restaurants all over - many waterfront. There is more cruise traffic there since the Megapier is just north of downtown but you don't see them much. People are super friendly and if you see the girls in school uniforms, ask them for directions (even if you know) they love to show off their English. Fun for both parties