How to teach my foal?

The short answer is this: now that you've had these two (or more) badly failed attempts, you need to get someone who's well experienced with handling foals to undo what you've inadvertently taught her (to fear people, to resent people and to show aggression to get them to leave you alone so you can be in peace with your Mum!) The sooner you get someone over to patiently correct her, the better!