In one of Kishimoto’s interviews he stated that Boruto’s eyes are more gentler because he’s not a fox, and since Himawari’s eyes resembled her father’s and are more fox like, I thought that it would make a lot of sense for her to inherit some of Kurama’s chakra.
So I combined the fox’s chakra with her mother’s twin lion fists to show the unique power of both her parents. She would also become Naruto’s successor as the new vessel for the nine tails.