Keep in mind the bigger picture, which is that the typical child of her age does not have much in the way of study skills, nor does every child enjoy memorizing. (I have only one who does.) In fact, the principal function of middle school (which is her current age) is to teach students executive functions (study skills and other related organizational and self-regulation skills) and social skills. She appears to be very much on track with her age-peers in this respect. It's as well to remember that just because a child is advanced in one or more areas of cognitive and/or academic development does not mean that they are equally advanced in all other areas, including executive functions or social-emotional development. Independent study skills are part of the larger package of executive functions that she will be growing into over the next several years, just as she will be learning personal responsibility for self-care, helping around the house, and maintaining and repairing relationships.
Also, is it really study skills that you are describing, or only rote memorization? Conceptual learners quite often dislike rote memorization as a study strategy, since it leaves their preferred learning channel idle while forcing them to use an intellectually mundane brute force approach. I noted that one of mine would memorize, but all of them prefer conceptual learning, which fills a need in their pattern-seeking brains better. If you find that lack of fluency in these skills is impeding her progress in math, I would suggest looking for patterns in them, and trying games. When we were children, my sibs and I used to play (and invent) card games that used mathematical operations of various kinds, with increasingly sophisticated manipulations as we became more skilled at math. My own children played a variety of math apps for fact fluency as supplements. If her siblings are a year or two behind her in math, you could also ask her to create some practice activities for them, which might be a fun way of giving her the lead in teaching others--which nearly always results in a higher degree of mastery for the teacher.
