If you haven't noticed, women are built different than men. As kglitch stated, you need a holster specifically designed for women. OWB holsters designed by and for men tend to push the butt of the gun into the ladies ribs. Be aware that with lowrider pants the waistband will not be high enough to keep the pants up without a good belt.
Women also have a shorter torso than men. That means that with a usual male designed OWB the butt of the gun will be high enough that women will have an issue grasping the butt.
Mitch Rosen make a OWB holster designed specifically for women called the Nancy Special. It's pricey, so it may not be the best choice for someone that does not really know what they want, but the craftsmanship makes it well worth it.
The two types of holsters that are actually better for women than for men because of the body differences are the cross draw and shoulder holster. Most women can take their right hand, wrap it across their chest, and almost touch their backbone on the left side.
Against my preferences, both my wife and daughter have chosen to carry off body in a designated purse. It takes special care, but at least they do not leave the gun at home.
