did your neighbor have a Glock 43? If not, let her try something like that as it may be more manageable (single stack vs double stack)
something else to consider: if you have a G23, you can buy a 9mm barrel and mag and easily shoot both calibers in less than 2 minutes.
- ammo was cheap online (not sure about currently), but there are several sites that track ammo cost per round
- blue label is a great deal (and now available to eligible veterans)