I don't know what your budget is, but have you looked at folders? My good lady is 5"1' and about 90 lbs, she rides a Brompton 6 speed and loves it because of:

- Simple gears
- Step through frame
- (Fairly) light
- Looks cool

She had a 21 speed touring bike before, but found the sheer size of the thing unmanageable (the frame was actually the right size for her).