*Yes, I know some princesses don't fit these requirements, but they are often said not to deserve to be in the line-up, and for reasons included in the poll. You can take that into account or ignore it when you chose.*
I don't think this really affects the character very much. It does affect marketability to an extent, but I think the others do so more. And I'm not picking Princess by birth or marriage because I think the princess should be a princess OR the protagonist of her movie. But just my two cents.

This does not really matter much, since the princess formula is changing more and more (with less films being a musical), and this does not determine a reason why a character gets to be a DP. It just has little to no impact.

I enjoy redemption stories..

Why did any choose being a princess by birth or marriage? Uh, news flash, it is the Disney Princess franchise. All members should be princesses! I realize Mulan isn't, but she saved China, and the Emperor bowed to her, so I guess there's an exception.

I feel like singing is an important part of being a DP. I know Merida doesn't sing but I still thing she shouldn't be a DP. Anyways, as long as they turn good in the end, I don't see this as a problem.

And Never serves or acts as a villain in her movie.

This isn't so important!