I am so sorry for this friend of yours. She will eventually lose the man in the end. One, her fear will happen. Fear is a magnet, it attracts what one fears. It is a law of nature to teach us TRUST.
Secondly, your friend lacks confidence in herself. Her behaviour is controlling because she believes she doesn’t deserve the man. Whatever she believes will also happen. Let her start reading books on living a life of gratitude to attract the best.
She still needs a long way to go in experiencing. I wish her a pleasant journey.