It's not just arm length. It's about effective torso length, which has to do with the reach of your arms, your actual torso length, lower back flexibility, etc. A lot of long waisted people need to sit more upright for lower back comfort and even though the torso is tall, the effective reach is shorter than another person their height.

Femur length may also be a factor. A woman with longer femurs may need to sit back farther to get the proper knee position relative to the pedal axle, and thus the bars get even farther away.

The best thing is to go sit on a bunch of different bikes. Women's components like bars and saddles can be added easily to a regular bike.

If the top tube is too short, you may feel stiffness in your shoulders (you may tend to hunch the shoulders to have straighter elbows and take weight off your hands and pressure off your triceps), or you may feel that your elbows are in your lap, or that there's a hunch in your back.