There are not that many womens heart rate monitors when it comes to design, size and comfort. Most heart rate monitors, even though they are supposedly unisex, are primarily designed for men. Women often have smaller wrist sizes and prefer more elegant designs, but these are often not taken into account. Still there are a few models specifically intended to address this problem.
Below is a compiled list of women heart rate monitors that have been featured on this web site. It is by no means an exhaustive list.
This shortened list is merely intended to provide the starting point of your investigation, especially if you are short of time. You should not rule out other monitors not on this list as they may well have other features that you will find very useful.
If you are a beginning/intermediate exerciser then take a look first at the Nike Imara, Polar F4. If you want more features than are available on them, then have a look at the Polar F6 and Polar F11. These 4 monitors are all very popular heart rate monitors for women.
If you can do without continuous heart rate monitoring, take a look at strapless heart rate monitors. They are very popular among women too.