Is admiring a married person, without speaking to him or seeing him except rarely, while trying to get rid of these feelings and praying constantly, considered forbidden in Islamic law? Is it considered a betrayal of his wife? And what is the solution to get rid of these feelings?

If the attachment of a girl's heart to her cousin's daughter's husband was not earned by her, and no forbidden act resulted from it, then there is no sin upon her, and she is not considered a betrayer. She must push away these thoughts and seek refuge in Allah from the accursed Satan, as Allah Almighty says: "And if an evil suggestion comes to you from Satan, then seek refuge in Allah. Indeed, He is the All-Hearing, the All-Knowing." She should strive to marry a righteous man.