How much of a budget? Bonaire waterfront - places with decent snorkeling - Buddy Dive, Habitat, Den Laman, Sand Dollar condos - maybe Eden Beach - are going to be in the $1500/wk. range Staying off the beach inland might be too far to walk. Of them only Eden Beach technically has a beach:
Edenbeach
There's a little strip of sand at Den Laman:
The higher ironshore seen in the left corner is the start of the Sand Dollar property it extends thru to Buddy Dive and Habitat.
Buddy's covers their ironshore with sand - you use ladders to get to the water.
Some of the more affordable places are in town also but there's no beach or snorkeling there. And now cruise ships. Most of the condos/resorts south of town in Belnem aren't on a beach either - it's ironshore. Usually steps/dock to the water but I don't recommend that area without a car as there's no restaurants within walking distance due to the lagoon south by the airport. It was a 5min. drive from there to south Kralendijk - the closest food was actually at the Plaza Resort.
Plaza Resort might be another option -
Snorkeling in Bonaire | Plaza Resort Bonaire They do have a beach with a breakwater to keep it in place. There's a lot of it, some places it's over ironshore - others its sand to the waters edge. Rooms are pricier though.
The Divi has a
small beach (manmade?) - and snorkeling just off the resort. One of few places close enough to town to walk also - I read their inshore reef was trashed in a hurricane a few years ago. Watch the animation on their site, one of the shots will show the beach.
Divi Flamingo Beach Resort & Casino Bonaire - Divi Resorts
Some of the best dive sites north and south of town are also good snorkel sites. At many the reef is 15' offshore. The defacto dive vehicle in any Bonaire dive pkg. is a 4 door small truck so maybe she could find some divers willing to let her ride along. Actually they might appreciate that as unattended vehicles get ransacked regularly while the divers are in the water. There are absolutely no facilities at any of the sites so she'll want to bring water, shade etc.
Roatan might be an option. Cocoview or Fantasy Island Resort(s) have great snorkeling just offshore.
Roatan Snorkeling | CoCo View Resort Afaik CCV has a small beach area. Fantasy Island has 3 beaches.
Fantasy Island Resort Both are full AI's and kind of isolated - just across the channel from each other.
In the West End - Half Moon Resort
advertises some of the best snorkeling in the Caribbean is just off their property. We did often see people out there when we rode by on our boat. They're a 5min. walk from the West End also - cheap food and everything else can be found there. She could actually snorkel from Half Moon Bay Beach out to that area also - probably 75 yds. or so.
Half Moon Resort, West End, Roatan, Honduras. Beach Hotel
A little more upscale might be Luna Beach Resort- in addition to being a full AI and having a
snorkel zone off their beach, they also offer a snorkel package with 3 daily trips to shallow spots nearby.
Paradise Snorkel Package Rates | Luna Beach Resort Just under $1000, dinner is extra.
It's a long walk to the West End from there but they have a water taxi for other food/entertainment. Other inexpensive food and lodging options nearby:
Bay Islands Diver Home