Oh my goodness. I feel so bad for you. I think you should take them back and ask her if this was her first job. If it is I would offer to stay and help her. That way she might be a little less intimidated by an unhappy client. Some times its better to go into a situation like this with honey in hopes that a second chance will be all she needed and then never use her again. If you loose your temper she may just close the door and you will have to pay for somebody else to fix it.
I am so sorry that this happen to you. I know I would sit down and cry and then be angry and then gather myself up and remember to be nice just to get what I paid for.
If you cant get her to fix the wrong just remind her that word of mouth can also work against her.
No matter what happens good luck.