Yes, it's too small for me at 5ft8.5 with long legs, unless I wanted a really aggressive fit. I imagine your partner would ride a very small (e.g. 15 inch) modern MTB, but with the horizontal top tube, shorter forks and short headtube of a 90s bike, you would want to size up to get comfortable. Worth checking her cycling inseam - floor to crotch . The standover height on this would be about 70cm, with 26x2.0 tyres. That's a guesstimate based on common BB height for 90s mtbs, plus 18 inches, minus 1 inch as the seat post extends above the top tube for the clamp.