Near Constant Anger and tantrums from 4 year old girl

My 4 year old girl has been dx PDD-NOS (mild autism spectrum).  She also has Sensory processing disorder, and a few other fun things.

She has not been an easy child to parent but we love her more than life itself.

However, lately, she is so angry and screaming most of the time.  The tantrums are WORSE than ever, worse than at age 2 or 3.  She is SOOOO angry over the littlest things all of the time - if something is in the wrong place, or i gave her the wrong plate with her food, or wrong color cup, or her toy was knocked over, or something was not in the right way...etc....she seems like she is mad or unhappy about something most of the time.
She screamed for forty minutes straight at the local chrismas light parade tonight because she wanted to RIDE in the parade, NOT WATCH it.  No matter how much I try to explain why we cannot ride in the parade, it does not matter.  She screams and screams.  At times my husband and I get so stressed over her tantrums that we give her time outs.  She has never been spanked, or hit yet she hits us, pulls our hair, and scratches us when she is angry.  It is frustrating to say the least.  Sometimes I get down and wonder if she is ever going to be a happy kid like she used to be.  We seem to go through phases, and this is a bad one.
Does anyone have any advice?
She see's docs, occupational therapists, goes to a special ed preschool, takes vitamins, takes omega 3's, etc....so we think we are doing everythign we can.

thanks for listening
angi

[24me]

The only advice I can suggest regarding her preferences, is telling her in advance what you will be giving her; cup, plate, food, etc.  My son is only 2 1/2 and has  been evaluated for his sensory processing. He also freaks about things that are not under our control. Most of it typical for a boy his age, but he also displays 80% of the other signs/symptoms.  I can sympathize.
This is very difficult for you I'm sure, hang in there. Most of the time you have to ignore the tantrum, eventually they will have to adapt. At her age she will learn that she has too. Be strong.