Oh I get it...

I'm the bad guy, I'm the bad guy!

The verdict: bitch or not?

The case:
I am a pretty harsh person. My nieces and nephew are usually very disciplined by me when they are around me. Well, I try to. I am not sure if I set them up for failure. Last night, my niece was being a bit of a shit. Whining, crying, for no reason. Well, she believed she had a reason. She wanted to take this "My size" Barbie that one of my cousins gave her to her house, but my sister didn't want any more toys. Anyway.

We are eating and I said, "Whoever can finish their dinner without talking will get a treat." You know why I said this. To get them to be quiet. She started talking a few minutes later, so she lost the game. My mom and sister were upset because I said she couldn't have the treat. My sister told me later we put too many conditions on her, and I told her, "This is not about the treat. This is about listening." My niece will be 6 next month. We have to ask her about 3 times to do anything: turn off the tv, come to eat, out on her socks. Ask her to come for a treat? She comes running! She has filters for her listening skills. I am trying to get rid of those. And being consistent is what is going to help. She would never take me seriously if I just give her a reward even if she didn't complete the task. Anyway, she's not entitled to the sweet, she wants it. She also didn't earn it. Is this a lesson I am trying to teach her at too young an age? Or am I just cranky because I am an old lady or lonely?