I'll answer for that since I learn Aikido. Although I don't learn it in a class or anything, I understand the basic principles and moves for it.
To put it simply, Aikido is a art where not much physical strength is needed. This art teaches the students on how to use the attacker's strength against that person. However, this art is created not to harm someone. It's main focus is to protect the practitioners while not harming the attacker.
Since you are a girl, this should be good as it don't really need much strength to use the moves. However, it don't really prepare you for real-life situations and you can't really use it to injure another person. As I stated earlier, the main focus is to defend and at the same time not injure the attacker. So, if you are looking for a martial art to defend yourself completely in real life, I suggest you don't take Aikido. But, if you just want to learn to know how to block and use the attacker's strength to your advantage, go ahead and learn it. No art is bad but you got to look at the situation you're in.
In my experience, I rely on Aikido not as much as I rely on the other arts I learn. As I live in a dangerous place, I am more focused on surviving and making sure that the opponent can't chase after me after I beat him/her up. Aikido is good only in blocking sense but if you need to stop the person completely, this isn't the right art to learn.
I'll say one good thing for Aikido though. It helps you relax and it has focus on the mental training as well. That can help you to focus and be calm in a dangerous situation but it won't help you much if you can't throw a punch or a kick well enough.
Hope this helps! I'll try and find a martial art that would suit you most.