Everyone needs to be able to do a full chin-up, women especially. If you can't, then you need to start trying right away. There are no excuses here, women are every bit as capable of performing this exercise as men, period.
In my experience, the best way to start doing full chin-ups when you can't even manage one, is to do resisted lowering first.
Start by standing on a bench or a chair that lifts you up to the chinning bar, take a good grip on the bar, then step off the bench and try to hang for a second.
Next, try to slowly lower yourself down to the floor. This may not be slow at first, but keep trying and eventually you will get to the point where you can slowly lower yourself all the way to the floor.
Do this as many times as you can in a row, and then once you can complete about 10 controlled lowerings (is that a word?) then try and pull yourself up once.
By doing resisted lowering (or eccentric contractions as we call them in exercise physiology) you actually build more strength than during the concentric phase (or lifting of the weight).
This is why it is so essential to slowly lower your weights when you are doing reps, and not simply dropping them back to the start position, you will miss out on some of your best possible gains.