If you want to enter the school through the independent enrollment quota of Wuhan University, with all due respect, your sister's "English is very good, ranking in the top five in the school, but other subjects are average" is not very promising. You have to think that there are many schools where the students with the top total scores are finally admitted to Wuhan University. Those students with the top total scores are definitely among the best in single subject.
As far as I know, there is no second batch of admission. (I am a student of Wu Da University)
Regarding the question of minority languages, your sister had better go to the teachers or leaders of her school to find out, because many schools recruit minority languages in advance (before the college entrance examination). It must be recommended by the school and then take the exam. However, colleges and universities in each region recruit different numbers every year, and the number is very small. For example, in the year of my college entrance examination, Beijing Foreign Studies University only recruited four Wuhan people in Hubei. However, because the number of places recommended by the school is also limited, it has something to do with how many people our school recruited in that year.
Finally, my suggestion is that your sister should try to work harder on other subjects. Try to go to a better university to study English.