I am a good Muslim and I live in America with my family. I have a cousin in Yemen. He's 19 years old and I am 15 years old. I always dream about him most of the time; I dream that I married him and stuff like that. I love him so much and I said to Allah that if he will be my husband then let me dream about him so I did and then I wanted to call to my grandpa in Yemen and I prayed the Isha and the last Raka'h I said O Allah if my cousin will answer the phone then let me know he will be my husband and all the dream that I dreamed it will come true, and then I called and he answered the phone. Is this from Allah and will it be true? Thank you and my Allah bless you

Praise be to Allah, the Lord of the World; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Supplicating Allah Alone is among the best reasons to have one's goals achieved. 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].
Know that asking Allah for something that contains a sin or leads to sins is not permissible, since Allah has forbidden going beyond the limits in making Dua. Allah Says (interpretation of meaning): {Invoke your Lord with humility and in secret. He likes not the aggressors.}[7:55].
Therefore, it is not permitted for this young girl to pray to Allah that her cousin be the one who answers her telephone call in order to enjoy his voice which probably could excite her sexually.
Also, his talking to her over the phone is not a sign of her supplications accepted, this is nothing but fantasy.
We advise this sister to try to get closer to Allah by following His Commands and abstaining from His prohibitions to have her supplication accepted. She should adhere to Sharia by keeping on praying and doing good deeds asking Allah to provide her with a pious husband who can share with her a happy life. That good husband might be this person or someone else.
She should know that what Allah Selects for her is more suitable than what she selects for herself.
To conclude, know that Muslims are obliged to take only the lawful means to get what has already been written for us by Allah.
Allah knows best.