Is it permissible for a married woman to pray to Allah to unite her with a man she loves in a permissible way, even though her husband is faultless, believing that Allah is capable of this without causing harm?

Attachment to a foreign man is a betrayal of your husband and a transgression against trust. Praying for Allah to unite you two is not permissible and is an excess in supplication, because it can only be realized by your husband's divorce, death, or khul'. Requesting a divorce without a valid reason is forbidden, as the Prophet (peace be upon him) said: "Any woman who asks her husband for a divorce without any harm (afflicting her), the scent of Paradise will be forbidden to her." Allah alone knows what is good; what you perceive as good may be evil. Therefore, you must cut off all ties of attachment to this man, fear Allah regarding your husband, renew your repentance to Him, strive to strengthen your connection with Allah, stay away from apparent and hidden sins, and pray for blessings for your husband and affection between you two, and that He protects you both from tribulations.