Just thinking about teenage and bodily changes and thought of the fantastic film Ginger Snaps. The two sisters, the lead characters, are in the girls toilets and the younger one starts changing into a werewolf! There's (lots of) blood, which her sister assumes is her first period. As she contorts, grows hair and becomes a werewolf, she gasps "Is this normal?" to which her sister matter-of-factly says "Of course!" I was 27 but it still resonated!!!
IMDB has the following: Ginger Snaps is a 2000 Canadian supernatural horror film directed by John Fawcett and written by Karen Walton, from a story they jointly developed. The film stars Emily Perkins and Katharine Isabelle as Brigitte and Ginger Fitzgerald, two morbid teenage sisters whose relationship is tested when Ginger is transformed into a lycanthrope (werewolf) after she begins menstruating.
Might be a useful thing to watch for younger women :-) "Despite modest box office receipts, the film was a critical success. It has since amassed a cult following and has been reexamined for its feminist themes." (IMDB again)