My personal under pillow weapon is my Glock 23 loaded with Federal Hydrashock 180 grain .40S&W. I also have a set of heine night sights and a Surefire X200 tac light. To be honest, I would stick with atleast .40S&W for knock down power. I would deffinately stick with the Glock or Smith and Wesson M&P series, seeing how your mother may end up using it. Most personal defense rounds are also made to not over penetrate too. That means you won't have stray rounds going every where, and if you hit your target, the cavitation will be greater.
Glock models in .40 - 22, 23, 27 and 35.
Smith and Wesson - M&P40
I'd go out to Blackwing since you're in Marysville, rent atleast those 2 and shoot them both.