Sibling Rivalry

C has been acting out for reasons that escape us all. Temper tantrums, floor kicking, screaming, utter rejection of anything M or I say or do. I feel like I have a teenager and a two year old living in the same body. Not. Fun. Is any one else with an almost six year old experiencing this? Is it a developmental thing or and issue????

Anywhoo, A has been taking this all in, and decided that SHE will be the good child. So anytime C refuses to eat something, she gobbles it up and announces "I LOVE it! I am a GREAT eater! Look at me C, I LIKE it!" Or, this morning, when they both woke up at 6 am and C pitched a fit because I refused to go downstairs until at least 6:30, A, who generally is the one insisting on going downstairs, crawled into bed with me and announced "I'm just happy to snuggle with you mommy. I'm being good!" Which, of course, sent C into an even bigger tailspin.

On the upside, at least I have only one child who acts like the world is coming to an end at any given moment. On the downside, I have a feeling that A is not helping matters and I'm unclear how to address the issue with her, or if I should even try to...