Jesus,our Lords peace be whit You.
Well well. It is not a sin,as such,but we need keep in mind that every ever so short prayer,is us talking to God,waiting for a ansver. So the elements to a sin is there. But,God gave us free will to choose,and that goes to every thing in life,so if she will fall in love whit You is not because You prayed,it is her free will. We can,and we both need and must,pray for others,and what we pray for can’t be a wish that something evil or bad will happend to someone else,and I don’t want to take the hope from You,but she might feel love for someone else still feeling friendship towards You,so if You pray for her to fall in love whit You,and by the way,it don’t work,I have tryed,as I guess most of us,may,and I am not saying that You mean bad,or want to hurt someone else,will be against someone elses will and hope,and then Your prayer means something bad for someone. But,as I wrote,God has give us free will,and she might choose You,or not,but I would advice You to NOT pray for such a thing,just to be sure You don’t hurt anyone,including this object of Your desire.
I remember my first love,the “real” love,times before my call to prisesthood,and my mistake by not follow it and marrie,and divorce,and now I have my call,still,but no way to become a priest. It wos a beutifull girl whit golden hair and clearblue eyes,and we did date for three days,I wos 15 and she wos 12,I never forget those days,and sometimes I still feel for her,but I lost her,we stayed friends for many many years,good and true friends,to alcohol and drugs,and I saw a picture of her a some time ago,and,well,I did see those eyes,and the rest wos gone thru years of using drugs and alchohol,and I when I wos younger did pray she would still fall for me,and priesthood call or not,I still wish she would be my friend,if not anything moore. My call makes it impossible to date,but I can say honestly that I still love her.
But You are young,and You will find someone else,marrie and get children if God so wants,and You will be happy.