Yep, different setups as you say from dual headlight Roadster or earlier Stds and Classics hand levers but R3T has the same front brake reservoir / master cylinder set up as the Thunderbird, so a Thunderbird may have adjustable levers... I have never checked but got a Thunderbird front brake reservoir/ mc for my project R3T.
I have not looked at the Thunderbird clutch side to see how it compares to R3T version.
I have some NOS sets of chunkier chrome accessory R3T levers but not sure if they would assist your wife.
LEVER KIT, PAIR - CHROME A9738158
Levers Kit Triumph ROCKET III TOURING
partsss.com
1 Levers Kit, Chrome A9738158
2 Lever, Brake, Thick, Chrome A9730154
3 Lever, Clutch, Thick, Chrome A2046446