I have found that being known in my area as the "resident gun guy" I get this type of question posed to me quite often. Mostly people Just want you to give them a make and model number so that they can run down to the local gun store and buy "their perfect gun". Gr8oldguy is correct in that there are a lot of considerations that need to be taken into account. A little research and leg time, really will affect the eventual outcome. It seams from your post that you are doing that.
Since you state that you are going into this with some level of physical disability considerations, I would suggest that you will have better end results if you make the search more about the revolver than the grip at first. For instance the S&W models 36 and 60 have a slide forward style cylinder release, where the Ruger Sp-101 has a push button style. The Ruger Sp 101 is also noticeably heavier than either of S&W's. Finding the revolver that she likes and can operate best and then getting after market grips for it to tailor fit it to her hand might be the better way. Most name brand, good quality revolvers have aftermarket grips made for them by Hogue and Pachmayer. While some people don't like Taurus and Rossi, I do. I just try to stay away from their early stuff and most of their new revolvers come with the oversized rubber grips stock from the factory.
I generally don't like to recommend the big box gun stores like Gander Mountain and Cabela's because they undercut small local gun stores by selling guns at near cost knowing you will buy higher percentage markup items while your there, but they do usually carry a wider selection to play with to see what you like.
If cost is a consideration, don't be afraid to look at some good used guns. The S&W mod. 36, Colt Detective Special, and Ruger Sp-101 are good quality guns. Just make sure you buy them from a reputable seller and that they are in good shape.