What is the way to overcome the intrusive thoughts of mixing with men and the fear of falling in love with one of them, especially after these thoughts began to dominate an engaged girl?

It is necessary to observe Allah's boundaries and the regulations of Sharia in dealing with foreign men, to close the doors of temptation, and to seek Allah's help and strive against one's self to remove attachment to this person, while being cautious of obsessive whispers and not giving in to them.