Of course she is! She was Valiente enough to go against her mother, their traditions/culture and she was Valiente enough to face the consequences she would encounter because of the actions that she did.
Yes, she was. She defied her traditions and culture to do what SHE wanted. That takes some guts, if tu ask me. She helped her mother get rid of the curse SHE had put on her family. And she did it. She is very brave, hence the título Brave.
To be Valiente is not to stupidly rush into dangerous situations without a segundo thought. To be Valiente is to be afraid, but face it anyway. Personally, I think Merida is the prime example of bravery.