A newer 250ex would be a good quad for her. Plenty of power for someone her size and their reliable as hell. A friend of mine used to have an 07, it was a great little quad, just not very fast.
i like the 250ex and the 300ex but the 300 is way more noticable with that extra 50 hp. i rode one with a pipe. pretty nice i actually wanted it cause i liked how it sounded