I haven't formed a complete opinion of her yet, but we have a few things to consider.
The personality is 0/10, I understand a 8 year old child wanting to be Oden, but a 28-year-old adult looking at Momo and claiming he is his father is ridiculous.
She is pretty, after all she is Nami with the horn. That's why I don't value appearance too much. (2/10)
And she is strong, very strong. I can even say that as strong as Oden. But strength is what makes a character? (10/10)
For now, my rating is 12/30. But in terms of what's most important when i considering a character, she is empty.