As anyone who has ever studied ballet knows, going en pointe is pretty serious business. According to Dance Magazine, it requires years of building up muscles in your body, and there are special ballet slippers that help protect your feet when dancing like this. Dancers are cautioned about going en pointe too young, as many professionals worry that the strain on a body that is still developing can be too much.
When Rose goes up on her toes while barefoot during a party on the Titanic, it isn't only dangerous, but it also seems unlikely that she'd be able to pull it off. It's not long before she loses her balance and cries out in pain, falling into Jack's arms. Things could have gone a lot worse for the former ballerina.
As Rose herself says, she hasn't done that in years. We can assume she's had some sort of extensive training to have that kind of control, but, if she hasn't danced in a while, those muscles aren't very strong. She's lucky she didn't injure herself.
