the SR22 was probably a great choice in pistol. any pistol she is able to operate AND is willing to train with/use is the correct choice no matter of caliber or action etc. and she seems to already be doing that! awesome.
for the future readers of the same question, the glock 42 is really nice. (.380) my fiance is very "particular" about what she chooses to carry and what she enjoys to shoot. she loves her glock 19 to shoot at the range but doesn't like to carry it because it's too bulky for her and she likes to wear tighter clothing. She was carrying the ruger LCP for a while beacuse it's so small and easy to conceal but hated to practice with it as it would hurt her hands and she felt like it would jump out of her hands or blow apart. i don't care to shoot it much either. she wasn't confident in that pistol and she wasn't accurate with it either. I got her a glock 42 as an early bday present and she absolutely loves it. it is the perfect balance of conceal-ability and hassle free shooting. smooth trigger, very little/manageable recoil, prominent and visible sights, much more accurate than the LCP. she is now shooting at the same distance with the g42 as she does with the g19 (about 21-25 ft) whereas she was practicing with the LCP at only 15 ft and not doing so well even there. which is why, obviously, i had to get her something else.
Good for your MIL. Im proud of her too
Try some Hornady Critical Defense in the G42, you'll think you are shooting a 22LR.