Nope, that is btw one of the reasons I like her character so much. She isn't really into doing the soldier stuff, but she does it anyway because she feels she has to.

Nah. Merida on the other hand is a tomboy.

Idk, sort of? But she barely shown any tomboyish traits and also she seems didn't have preference about masculine stuffs until she joins the army.

More or less

To me, she seems in between being feminine and being a tomboy.

In-between.
She is not an epitome of tomboy. She didn't join army because she enjoys sports. I can see myself doing something she did in order to reach some extremely important goal( like saving a family member) or prevent something I afraid a lot. I would doing many thing to get something important. But I consider myself rather girly than tomboyish. Things I do just for fun are mostly girly.

I think that's why she doesn't fit in at the begining.