How can someone be kind but not nice?

Shouldn’t we be kind and nice? I mean I’m a kind and nice person, but I get disrespected when I’m so nice to people. My older sister always said, “I’m not as nice as people think. I’m not.” She will give you a stern direct look in the eye. She kind of scares me. She would say she she’s kind not nice. She gets more respect than I do. What gives?

She told me I need to stop being so fucking nice to people, quit being a doormat because being nice is poor, cheap and useless. That’s how people are going to see me and I don’t wanna look easy. Don’t expect everyone to be nice to me and men will see that I will be lose and cheap if I don’t say no to sex.
Damn that was very harsh…. my sister can be brutally honest and she isn’t nice about it. She isn’t a jerk though. She’s actually sweet but she only shows it to people that deserves it.

How can someone be kind but not nice?
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