How do I teach my Girlfriend PC gaming (specifically FPS) mechanics?

So my girlfriend expressed an interest in gaming with me and we have been playing games like rocket league and Ark with each other (she is unsurprisingly not very good as she has never owned a console/gaming PC until now).

She enjoys Ark and can gather resources & craft but cannot move well or aim/react to any threats so she is basically dead if anything hostile notices her. I think this is due to lack of muscle memory and not knowing how to move/aim in FPS style games. She presses W to go forward and when she gets to where she is going she rotates the screen using the mouse and uses W to go in the direction, same thing with looking up and down - she isn't using the keyboard and mouse in tandem but one after another.

She knows what to do because I've told her but it isn't working in practice. Has anyone learnt or taught anyone else to learn FPS movement mechanics recently - what worked best?