I worked for this company for 4 months and I was never written up or verbally warned until one day I was told that she didn't believe I was capable of doing my job and that I didn't want to be there. I was never told that I was let go or fired, I just asked if I am finishing out my schedule the next week and she told me no. I worked my 12 hour shift with no break that day and when I was leaving that's when she brought me to her office to yell at me. Is this a case of wrongful termination?

Jobs have the right to let you go for no reason whatsoever it is called at will employment.
At-will employment - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/At-will)

No, you were fired, this is how it happens.