In the eighties I and my wife worked for 4 years at Maldives as indttuctors and divemasters.
At the time there were no limits. Our tour operator allowed max depth 50 meters with deco, in air.
So, some dives were deep, long and in reef channels ("kandu" in Divehi, the local language), where currents can be really strong.
We never allowed our customers to use any kind of tether among them.
However we did allow to use reef hooks, which were used to get a grip on the edge of the channel.
Another type of dives was along inner reefs where the current flows in a sort of river.
In this case it was a drift dive, it was not allowed to get a grip on the reef, nor to swim against current.
We had simply to let the current carry the group of divers, watching the wonderful corals while traveling without effort thanks to the current.
My recommendations for your wife are based in my wife's experience (she also is a "natural").
Here is how she did dive, after experimenting various setups:
1) long freediving fins with full feet pockets and thin neoprene socks - proper flutter kicking without flexing the knees, same style as deep freedivers. Forget frog kicking, in those currents it becomes exhausting and not effective.
Preferred fins for my wife were Cressi Rondine Gara.
2) Very minimal and streamlined body protection: often she was wearing just an olympic-style swimming suit, sometimes a shorty 3mm neoprene suit. Never a full suit. No BCD (at the time it was not mandatory). Today it is mandatory, but I suggest a minimal-size rear-inflating BCD or a very small wing with a light backplate and nothing attached to it.
3) if you get steel tanks, probably she will not need any weights.
4) keep nothing dangling around: second air source should be strapped to the harness or with an elastic collar, better to avoid a traditional SPG and use an air-integrated computer. My wife also had a velcro strap keeping her power inflator attached to the harness.
After a couple of weeks of adapatation, my wife started to love strong currents!
We both struggled at the beginning due to using wrong equipment and propulsion, carrying with us too many things and not being properly streamlined.
Channels in Maldives is a typical environment where the phrase "less is more" becomes true.
