Your son is right, BTW, my daugther also has small hands...
She initially didn’t like the Glock grip (very few people do at first)
After she went to the range, used proper technique and shot it...she loves it...
The grip isn’t a problem. As a 1911 variant shooter (I have six). I recommended she buy the Glock for it’s simplicity, reliability and accuracy.
There are better guns for certain tactical situations but they require a lot of training and assume that you are in a ready leaning forward position.
For everyday carry for someone that doesn’t train regularly and wants an auto, I would only go with the Glock.
considering how many simple to use autos are out there I would not be so hung up on glock. Is she does not like the grip she should try something else. There are LOTS of other autos that are just as reliable and have better ergonomics. Off the top of my head the S&W M&P, the SA XDs and lots of good ones from Ruger. Heck, just about every brand now makes something in a nice polymer frame. I prefer 1911 and can’t stand the glock grip. There is a very specific part of the front area that just sticks out funny. Bugs me no matter what grip I use. My XDm fits my hand like a glove and is just as simple, just as reliable, and just as accurate. Telling someone to ‘only’ go with the glock’ is terrible advice considering the variety of polymer framed guns out there.