if she doesn't ride very often then you should start her off with something a little less strenous, keep it fun for her. i'm 5'-1.5" & 98 lbs and i run a 46x18 on my converted ss road bike. it might be a little too easy for me, but it's nice to be able to cruise. let her feel relaxed on the bike, she'll be able to enjoy it more. gosh, you're like a whole foot taller than her...