Rebelliousness: showing a desire or tendency to resist authority, control, or convention.

Or "Somewhat. I don't mind if it fits in with her character".

That's okay if a DP sometimes act rebellious. But not too much, she must can balance the situations that she can be act both of rebellious and polite.

I get annoyed if she's rebellious just for the hell of it, but with good reason for it, she should be a little rebellious.

As long as I understand her fully developed "motives" for being rebellious.

Oy. So, so sick of it. The only heroine I can think of who was rebellious for a very good, selfless reason was Esmeralda (unless you count Cinderella's little acts of rebellion like saving the mice or refusing to be broken, but I mostly mean outwardly). The rest of them just do it out of selfishness, which is rebellion in a nutshell.

though I think most people have different definition of what it means. I mean like Merida's rebellion, which was done out of spite and self-centeredness. many of them seem to mean it as "bucking an unfair system". although that's still pretty subjective.

She should stand up for her rights and needs and long-term decisions. It's her life eventually, and no one else will live it for her, so she might as well make the decision herself. Even if she were to regret it later, it would be her experience to learn from rather than someone else to blame onto for forcing a decision she didn't want to make in the first place.
I don't care about fitting with a character, but more for a justified reason.

Rebelling against things that are inhumane or villainous is completely necessairly in my opinion. The thing is that rebelliousness doesn't make automatically me adore a character. And some rules exist for a reason.