I would definitely tell her.

Please don't let your worries of what she thinks of you, like you mentioned, outweigh the implications of not telling her. If you or someone in your family was in danger, wouldn't you want to know? She can make the decision whether or not to do something about it, but you think she might be in danger.

If that doesn't convince you, if something did happen to her, would you be crushed with regret or self-hate or guilt for not saying anything?