((Off-topic, sorry: Venus... I've done the same thing "no thanks, I really don't need help lugging this 70lb giant suitcase down those stairs.. yes, I know that I'm ALSO dragging a 50lb smaller one at the same time, and yes, I know that I am also wearing a 15lb backpack... yes, I know that that is almost my entire body weight... no... no thanks..."))

You really do need to make things clear to her. And likely multiple times. It isn't her job to step in and do things for you, because she's not being paid to be your assistant. She's your girlfriend and I am sure that she wants to help, but she isn't trained or qualified to know how to help you. That's your job - to inform her and help her understand.