90s movie where girl finds out her sister is actually her mom?

I’m trying to remember the name of this movie! I don’t really remember the plot line, but it’s about two blonde sisters who don’t get along very well. The main character is the younger sister. It ends with her finding out that her sister is actually her mother (she had her at a very young age), and that her “mother” is really her grandma. She has been raised to believe her grandma was her mother.