i have a 24" cruiser that i ride. it's a vintage Colson, and there's pics of it all over this site. the motor fit perfectly, which means it was really tight, and i had to work at it to get it in there, but it fills up the space and makes it look like it was supposed to be there.
i've also got a laidback seatpost, so it puts me back behind the bottom bracket when i'm cruising.
i'm 5'7", and when sitting on the bike, i can have both feet flat on the ground with my knees slightly bent. it has the feel of a motorcycle, without being too short.
if this bike was pedal only, it'd be too small for me, at least the way it's all set up, as sitting down and pedaling is kinda uncomfortable, and feels goofy. not enough knee room. but as i just sit on it and let the motor do the work, it's perfect.
it could easily be set up for a smaller rider, and it seems like women have a tendency to ride in a more upright position (i guess they just don't like slouching like we do,) so without a laidback seatpost, the stand-over height would probably be perfect for her.
so, i'm suggesting a 24" cruiser. they're not as popular as a 26, but there's plenty of parts and upgrades available, and vintage stuff seems to go cheaper, since there's not much of a market for it. i've noticed a lot of new 24" cruisers on the market lately, but i don't pay much attention to bikes made after 1950...
(edit) my statement about women's riding position isn't meant to be sexist, just something i noticed. look at most women motorcyclists, and they all sit up straight. same with motorcycle cops...)
