The Model 86 Beretta was discontinued a few years ago. It is a single-stack, blow-back, .380 ACP pistol. They are often found in Pawn Shops, on-line Auction Stores, and in the used section of gun stores. The gun, itself, is almost duty-sized, with an alloy frame. It is soft-shooting, quite reliable, and accurate.
The 3032 Tomcat has had a checkered history in durability. Today's stainless version is much better than the blued version in that respect. It is also a single-stack gun, almost pocket sized, with a tip-up barrel in .32 ACP.
My wife is afflicted with early-stage RA in her hands. Thankfully, medication has arrested it prior to significant damage. When it was first diagnosed, she wasn't happy firing her usual favorites. She had been a serious adherent to the "starts with .4......" school of shooting prior to that. Today, she's back, but only to a limited degree. I can see where a person with a significant amount of damage from RA would be uncomfortable shooting just about anything that "experts" regard as a true "self-defense" caliber/gun combo.
Get her out to the range, and give her a number of guns that she likes, and let her shoot them. ONLY SHE can let you know what will work for her. Revolvers are not the panacea that many think of them as. Some revolvers triggers are going to limit her ability to function them. Not in just pull weight, but in the arc of travel. Rim-fire revolvers, for example, can have triggers too strong to be easily manipulated. Revolvers also seem prone to having ejector rods unscrew, tying up the action, or debris under the ejector star tying up the action. Then, reloading that little J-frame, or even a K-frame, is going to be much more time consuming for the non-dedicated shooter than slapping a new magazine into place.
The woman will be the deciding factor here. She needs a gun that will let her practice without pain, or that aggravates the RA. Once that's decided upon, caliber is less important. A miss with a .500 S&W doesn't hurt anyone but the shooter. A hit with a .25 ACP will hurt the recipient.