Also Pocahontas. Merida is a damsel in distress.

Why not Mulan? Because she has a moment where she needs to be saved by the main male character; if Shang hadn't stepped in she would have been executed.
Merida doesn't even have any men in her life apart from her father and her brothers.

Yeah instead Merida has her mother and brothers to constantly have to save her

She is the only one who never needs to be saved. Shang saved Mulan by not executing her when he found out she was a woman. He also trained her to be the warrior she became. Merida, even though she is a fighter, is constantly in distress.

Merida is one of the bigger DiDs (ironically.) She relies on others most of the time and needs to be rescued, really, rather a lot (and by her other and brothers, no less.)
Pocahontas never really needs to be saved, but she tends to wait for others to tell her what to do.
Mulan may be spared and protected by Shang throughout the movie, but she does the same. They work together. And, again, she protects and saves him as well, so why can't her protect her? Mulan is proactive, that is why I picked her.

Mulan and Pocahontas are strong grown woman who can take care of their selves and don't need 3 3 years old to save them

I agree with rhythmicmagic AGAIN. XD

I agree with TigerRanma :P

She's the only one who doesn't need to be saved out of these three.

Oh god you did not just ask me this! :O I think Merida, she fought off her fare who is double her height and weight to save her mum. Plus, she was the one who saved her mum form the curse