Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Supplicating and asking Allah is one of the most significant acts of worship.
Allah Says (interpretation of meaning): {…"Invoke Me, [i.e. believe in My Oneness (Islâmic Monotheism)] (and ask Me for anything) I will respond to your (invocation….}[40:60]. Allah also Says The Prophet (Sallallahu Alaihi wa Sallam) said: "Whoever does not ask Allah, Allah gets angry with them." [Reported by Tirmizi, and Albani said that this is a sound Hadith]
There are some conditions for a Du’a (supplication) to be answered: A Du’a should not request what is Haram, or a sin.
The Prophet (Sallallahu Alaihi wa Sallam) said: "The prayer of a person is answered as long as he does not make Du’a to commit a sin or to cut relations with relatives, and as long as he does not hasten the answer." [Reported by Muslim and others]
Making Du’a to Allah to marry a specific woman is something allowed and permitted in religion. Getting married is something allowed in principle, and asking Allah to get married is also allowed, even if it is with a specific woman.
In priority a Muslim should ask Allah to choose for him what is good and to ask Him to bless him with a wife whom he will be satisfied with, and it may be that the good is in another woman.
There is no harm in asking Allah to bestow upon her a good husband, this is considered a prayer of a brother (sister) to a brother (sister) (in Islam) when absent.
Our view is that you should release your heart from being attached to this woman, so that you would not be led to unpleasant consequences, or a cause for the heart to always be attached to her.
Allah knows best.