No, Amanda Bynes is not faking it. She suffers a serious psychological illness called Bipolar Disorder, and as a result of a major episode, she had a nervous breakdown. The media likes to portray individuals who have such as either "faking it" or "crazy", but the truth is she just needs help and is getting it.
No, I do not believe Ms. Bynes is faking her strange behavior. I think she is mentally ill and a drug addict and those two combined can lead to very erratic behavior. She is probably dealing with things that happened to her as a child star and lashing out because she doesn't know how else to handle it.