Mildred Hubble
Mildred Hubble is a major character in "The Worst Witch" children's book series by Jill Murphy. She is the protagonist in all the books. She is friends with Maud Spellbody and Enid Nightshade and has a strong rivalry with Ethel Hallow and Drusilla Paddock.
Bella Ramsey
Ramsey also stars in 2017 TV adaptation of "The Worst Witch" books as the title character, Mildred Hubble.