When tested on ballistic gel, the .38 penetrates through like 6 feet
Are you high?
and expands rapidly (it's a magnum)
Whether or not a bullet expands has nothing to do with being a magnum cartridge, it's based on the shape of the bullet, like hollow points or soft points
Also, .38 special isn't a magnum cartridge, you're thinking of .357 magnum, which is a magnum cartridge based on .38 special.
While there is a large debate about the best caliber for self defense ammunition, price per round shouldn't be a the top (or even any, imo) deciding factor when the ultimate cost is your life.
That's irrelevant tho because OP isn't looking for a self defense gun at the moment, just something to get used to shooting. So I'd say a .22 would be fine for that if she doesn't have a problem buying multiple guns for different purposes
