The problems with mixte bikes is that they are a. about 2 lbs heavier than the equivalent "men's" model and b. they were usually lower level models. If she is not particular for a mixte, you might want to take a look at early 80s Miyata 310S (Stepthrough frame) which weights about 25-26 lbs, compared to 30 lbs for an similar age Miyata 210M mixte