I can tell you now this is a touchy matter. If you get too big a bike, it may get loose from her early on and scare her into not riding. Too small and she could get bored really fast. My girl is 5'5" 120lbs and I bought her first bike a few years ago, I opted for an XR100. Along with that I knew I wasn't going anywhere fast next to the 100 so I found a brand new, never ridden 91 xr200 that I am waaaay too big for (I'm 6'2", just over 300lbs ). I knew we would be doing easy riding and I'm getting older so I have no plan to go balls out very much and I've owned LOTS of bikes in my life including a few XR200's so I knew what I was dealing with and the bike's limitations. the interesting part is we live in a very mountainous area and the closest riding area is only about 8 miles away. There are some pretty steep, rocky hills in this area and some of the hills scare the woman to ride up. I know how it is being a beginner so sometimes I ride up the hills, walk back down and ride that itty bitty XR100 with my big fat arse up the steepest hills. I'm sure it's rather comical but the truth is I haven't found an average steeper hill that the little guy wouldn't zip me right up on! My point is, and I'm not being sexist here, some ladies are not rough and tumble bike riders but DO love to get out in the fresh air and mountains and enjoy some outdoor motorsport fun. Watch your girl, read what her plan is. Is she trying to do little hops over hills? Is she already trying to challenge herself in small ways, testing the bike and her ability or is she just tooling down the fire road enjoying a cruise in the woods? Don't trust what she says either cause my girl acted like she was going to be the next Jeff Stanton and my gut feeling told me she was saying one thing but I knew better and am I glad I listened to that gut feeling. Just don't get her something that she can get in over her head really easy on, there's always other bikes later on and a long time rider almost always has the tale of the little crappy dinosaur they learned to ride on first (like my 60'S model Yamaha 80 with high/low range). The xr100 is a great choice because if she takes care of it, it will hold most of it's value later on.