Reread your post. "The firearm will be used for personal self defense, but I'm not really expecting a home invasion, and she won't be using it when concealment would be an issue. I just want her to have something portable that she can slip under her car seat and carry with her if it becomes necessary for her to take our daughter and beat feet from the greater NY area."
This isn't making sense to me. Is she expecting a five minute warning that she is about to be attacked or molested? Trying to locate something under your car seat is damn near impossible unless you get out of the car, bend over and feel around for it.
Unless you've got one of the special "holsters" than fits on the bottom of the seat, not on the floor under it. Then it's a fairly handy location. Unless you have really short arms for the length of your torso. I'm in opposite, "gorilla", configuration myself. :)