Jiu jitsu (which is soft) is sort of in a world of its own but definitely has a huge place in martial arts especially for a woman as the focus is on leverage/technique, instead of speed/strength. I'd recommend it in addition to one of the ones above if possible, but if not, it's not an acceptable substitution (for self-defense or fighting), despite what the Gracie's might try and tell you.
I'm going to elaborate on this, because it's an important point - that most people misunderstand.
It works in MMA because the rules cater to it.
If you ever get in a fight with someone, there are several reasons why jiu jitsu would not be helpful:
-You are (maybe) fighting opponentS. Jiu Jitsu has a focus on one on one. Going to the ground with bad guy 1 is an invitation for bad guys 2, 3, 4 etc to kick your head in. You might have gotten in a fight with one person, but didn't catch his buddy behind you.
-Jiu Jitsu relies heavily on extremely close quarters and is the strongest on the floor. That someone might have a knife or other in his hand. You are dead
-Jiu Jitsu training sparring works through a set of rules. Those rules are a great way to defend yourself against someone extremely close to you. That is, if the person follows the same rules. Someone who trains a specific style will go through the motions via muscle memory, this includes all the cons of the style. Some times those cons are a lack of defense versus strikes. What's to stop your enemy from putting his finger in your eye, headbutting you or other?
-Concrete is hard. It is very painful to roll on. Doing a flying armbar on someone is a guarantee that your head will be hitting the concrete first. Moving around on concrete is very painful, especially the hips, knees and elbows. Trying to do some of those moves/techniques while on concrete may be impossible due to the pain.
-Anything on the floor. That rock, that broken glass, that needle, etc. All are hazards. Are you gonna see them when the adrenaline is rushing through your veins and you're rolling on the floor?
-Escape. If shit hits the fan and you need to make a run for it, you're down. You have to disengage yourself, get up and run. Easier than it sounds versus a fighting opponent.
-Do you have what it takes? It takes ballz to break someone's arm and whatnot. When it comes to it, you might not have the testicular fortitude.
-The fact that your best defense is based on laying down on the floor.
-Self defense is not only about neutralizing a threat, but also by getting away from it. Again, running away should be a priority. Much more difficult to do when you're focused on going to the ground.
-Boxing, judo, wrestling, and various forms of kickboxing (muay thai, etc) allow you to engage your opponent without being attached to them. When you are doine with one, you can focus on the other. You can still be effective without being attached to one person.
If you're a woman, I'd stay away from Jiu Jitsu. Best advice I could give is work on your 100 meter sprint, and increase your kicking speed to the groin and knees.
A woman who is fighting her opponent who is probably trying to rape her will be at her weakest on the ground due to a difference in size, weight and strength. When it comes to the difference in strength, the biggest gap is that of upper body strength. Technique is important, but it is very easy/possible for a man to muscle through.
If it comes to that range of contact, I'd suggest she throw it all to the wind and start biting and scratching with the intent to kill.
They say that fighting is not about the style, but about the fighter. I would agree.
It's a mentality.
I'd focus on kyokushin, muay thai, boxing, judo and/or wrestling:
-Kyokushin and muay thai because they give you a focus on kicks, knees and elbows. Kyokushin has a huge flaw is that it has zero focus on punches to the head. Can be remedied with some boxing. The advantage to kyokushin is that all the hits are done without protection. So those punches to the body, and kicks/knees to the head are the real deal.
I don't know enough about TKD to comment. As long as it isn't the sport/olympic version, you should be fine.
-Boxing because it allows you to learn to roll with the punches and properly protect the head. Most people don't know that boxers wear gloves to protect their hands, not their head. Punching someone's head, especially improperly, is a great way to break your hand and make it useless. The better of a boxer you are, the harder you are likely to hit, and the more likely you are to break your hand. Ironic. So just hit with an open palm.
-Judo has a focus on 'gi', which is basically clothing. Being able to throw/manipulate someone by their clothing is very useful. Being able to throw someone without going down with them yourself is great for self defense. Gives you time to focus on the next guy and/or run.
-Wrestling. Huge focus on not being taken down by the legs and other. Has some good throws. Take into account the 'lack of defense' concerning standup fighting.
I don't have many credentials.
For what it's worth: I've done fighting 'sports' for a number of years (over a decade) in a variety of styles and have competed in a number of tournaments. These are just my observations.
Sorry for the rant.