What is the ruling on one who goes to the the mosque out of love for a person, intending to meet this person, and is their prayer accepted in this case?

If one intends to go to the mosque with the intention of praying, meeting righteous people, greeting them, and checking on their well-being, then this combines two acts of obedience, not an act of obedience and a worldly preoccupation. In the Hadith: "When two Muslims meet, shake hands, and invoke blessings upon each other, their sins fall away from them as leaves fall from a tree." And the prayer is valid even if a person intended a worldly matter by going to the mosque.