Frustration

Why do kids need to test their limits? I'd like to say sorry to my parents for pushing limits as a kid. Im sure I did it. Kayla at the age of 4 has really mastered pushing her limits. She has discovered how to stomp her feet, roll her eyes and slap her hands down to her side to show her frustration. Tonight she is arguing every little detail. We spent the day at the New Childrens Musuem, went to gymnastic class, played outside, planted new plants, a great day planned for HER! Now it is bed time (actually past bedtime) and she is pushing it. She comes out to tell me her music is too loud, she is hot, her finger hurts. I finally tuck her in for the 50th time and explain it is bed time and she needs to stay in bed. I told her she will not be happy if she gets up again. Yes, an empty threat I know. So 3 minutes later I hear her little feet come into the living room, "mom, you never told me what is going to happen if I get up again....you just said you will be angry, so Im up and what happens now" WHY!! Why does she push it. AHHHHhhhh...... Luckily Devon is still innocent. No temper tantrums yet, no fighting me, he is easy to lay down for bed. Kayla has the stubborness for 2 kids, if not more. Dont get me wrong, she is amazing, but boy can she push it! So where is she now? Shes standing in the corner. When I asked her what I should do since she got up again, she said put her in time out. Fine! Go! She has been standing there about 5 minutes. I just asked her if she would like to go back to bed. She said no, she will stay standing in the corner. Her toes are against the wall, her nose is practically in the corner...but she is quiet. Not arguing, not crying, not stomping, not rolling her eyes ( well at least I can't see them), so what am I to do. Can I leave her there and can I go to bed????