No Mutants Allowed

Also I'm having her wean in on the newer games but I'll have her do the old ones too!

Well, every one besides that one for original Xbox and ps2 (that I still haven't played)

Seeing as 3&4 aren't fallout games or at the very least barely resemble a proper fallout game imma say new vegas

I would say try Fallout 3 so that she wont refuse playing it after playing NV for the first time. NV is so good that it ruins the Fallout 3 experience. Trust me on that one.

I'd say that kinda the point of starting her on new vegas. Otherwise it's kinda like tricking her into playing trash.