Awww . .. . I'm sorry, what about leasing her out to a more advanced person?
Although this is generally a good option if she is not suitable for what you want to do then chances are she'll never be, and you might be able to sell her to someone who she is suited for and she can their forever horse. I don't know your relationship with your horse though, but you don't seem great.
Horses have mood swings, mares especially. If you are looking for a more even tempered horse look more at the geldings, although remember each horse is different. Mares are generally more dominant and moody though.
I think you need to figure out what the problem is. A clumsy horse in the ring might not necessarily be a bad jumper, she may just need more work in collection, rhythm, gymnastics etc. To be successful you have to work at these things, so figure out if the performance problems are really her problem or your problem.
As for attitude, you won't know if you get on with a horse for a while (generally) so a new one might not be any better. If she tries to "kill you" everyday then maybe its the way that you handle her that causes you not to respect you.
My advice would be to work out what your problems are, perhaps get a good quality SJ trainer to do a lesson with you so that she can evaluate your horses potential. If you come to the conclusion that the horse isn't suitable for you for whatever reason then consider selling her if that is what you want, but if its just something that requires work, be aware all horses are like that. Don't quit just because its getting a bit tougher.