don't worry about frame material.
aluminium is fine for touring.

most important is fit. more likely to find a
suitable small frame mtb for the little lady.
sloping top tube be good for short arse gf's.
did you take your hunny to try the fit?

mtb's w/rigid forks make nice touring bikes.
put on thinner road tyres.....26x1.5's.
lighter, faster, may even lower standover a bit.

got an address for that 3-storey townhouse full o'bikes?
take any cellphone pics?
i might wanna do some shopping......