[RWebb]

thieves will use a ladder to access 2nd story windows, esp. if you are out of the house

if you need to leave the windows open more than a crack, you will need to buy some gridwork to put up - there are different styles to match your house style; be sure to use a special can't easily remove type fastener system

cheapest way to deal with windows open only a crack, is to drill some matching holes and put a nail, etc. thru both holes - above pics show nicer looking solutions

pistols can be turned on the owner by an intruder, so you need to take steps for that

can your niece handle the recoil of a .45? better find out

a .45 does have some advantages, but so do 12 rounds from a Browning 9 mm

if she is resistant to a course, start here off with a pellet pistol at the same place, then move her up to .22 shorts & so on - you go with her, or some other relative/friend