Almost 2 and already got attitude!

I know she looks all sweet and cute in this photo and for the most part she is but boy, oh boy, has she got sass! Sometimes I have to look the other way as she's giving me attitude because it can be pretty funny. Other times, I have to walk away and remind myself that she is only 2. And where did she learn to scream? Do little boys do this? How is it that little girls always learn how to scream? Emma has really enjoyed practicing screaming lately. Not out of anger or frustration, well sometimes, but mostly just to hear herself and see how we are going to react. My biggest challenge is figuring out what to do. Is she old enough for time outs? Or are these fits and tantrums a stage that parents of 2 year have to endure until they grow out of it? I've been meaning to check out some books on the subject. Any recommendations? And what about church, at what age can we realistically expect a child to sit quietly? I realize that all kids are unique and develop at their own rate so the answers to my questions are probably varied. One thing I find interesting is that the tantrums usually only happen in front of her dad and I. She seems to be a sweet little angel when we're not around! Despite the tantrums and screaming, I absolutely love watching how much she is learning. Her language has blossomed so nicely lately! It's fun to hear her say her little words, like "peetaboo" instead of peekaboo and "quackoo" instead of cracker. I just love her to pieces! She really is sweet. I am so, so glad that I get to be her mom : ) I'd love to hear any words of advice or cute stories that you'd like to share!