This took me way longer to finish than it should have.
So, although the movie shows her vain, selfish, and villainous side, I wanted to capture those nurturing and motherly moments that Mother Gothel must have had with young Repunzel. These things are hinted at in the first song Repunzel sings where she talked about knowing how to read books and sew. Etc.
It's also obvious that Repunzel does love her step-mother, so she can't have been treated too horribly. And Mother Gothel also kidnapped her when she was a baby, meaning she had to care for and nurture her.