Wing Chun is a nice place to start. It was developed by a woman, so the story goes. I'm about the same size as you, and when I took Wing Chun some years ago, I felt like it was a good fit -- not that I have any thing to compare it to, but I do feel that it is something I will go back to at some point, if/when my life settles down a bit more. My reasons would be not so much for self-defense but just because I enjoy studying a form of movement and the sense of balance that I gain from it.
I think we've had this conversation before, but it bears repeating, and I'm sure Trek420 is much more eloquent about it than I could ever be -- the martial arts can offer you a great deal beyond self-defense. There are physical, emotional and for some people even spiritual benefits that can be gained from a lifetime of practice. Self-defense is a great reason to practice a martial art, but it's not the only reason.
In the martial arts, when you spar/fight/compete it is generally within a framework of agreed-upon rules and mutual respect. If you are being attacked by someone who is determined to cause you harm, it is a different ballgame.
In regards to self-defense, which is NOT the same as martial arts, you may be able to find a good weekend workshop/short course that focuses on self-defense for women. Some police departments or community colleges or other community organizations may offer these. They should teach you how to break holds, how to assert yourself and communicate to an attacker that you are more trouble than it is worth. How to hit back with everything you've got and not telegraph your punches. And most important -- if you have the opportunity, steer clear when your spidey-sense is tingling!
If reading about others' experiences and trying a beginner class or self-defense class whets your appetite for practicing a martial art, wonderful! If not, some basic self-defense still gives you some tools that you will hopefully never need.
For my part, I've been thinking about looking for a first aid course. I haven't taken anything like that since high school, maybe it's time for a refresher.