Is it permissible to communicate via WhatsApp with a girl to propose to her, express love to her, and obtain her father's phone number, especially if it is difficult to reach her family through traditional means, and is this considered necessary to alleviate psychological suffering?

There is no blame upon someone who loves a woman and keeps himself chaste. Marriage is best for one whose heart has been touched by the love of a woman, for it extinguishes the flames of passion and promotes chastity, and because "we have not seen anything better for two who love each other than marriage." It is obligatory to ascertain the woman's righteousness by asking trustworthy individuals about her before proposing to her. There is no harm in sending her a message expressing your desire to marry her, within the bounds of Islamic etiquette. It is preferable that this be done through an intermediary. You may obtain her father's number to communicate with him. If marriage to her is not possible, you must completely turn away from her and strive to forget her.