If you know your own second hand components work, that's half the battle. Buying complete is a risk. I'd be inclined to go steel rather than Ti, but the concept is sound
Any reason for steel over Ti? Cost/benefit? I've always fancied a steel hardtail but I'm worried about the extra weight for the Mrs (albeit only a 16" frame).
I don't think it's sensible with her height.. only because I'm guessing she's around my height if she's on a 16" frame and I would never consider a 29er. I'd sell any parts you aren't going to need for extra cash and buy new (steel over cheap Ti) and go with 26/27.5.
If you know your own second hand components work, that's half the battle. Buying complete is a risk. I'd be inclined to go steel rather than Ti, but the concept is sound