Permissibility of marrying ones student

1) i am 25 and the girl who is my student is 15, i am her tutor. i have feeling for her for many days, and i like here, i want nikha with her with islamic sunah, but i dont know what does she think for me i did not tell about this. i am very depressed about her, and not concentrating in my life. the feeling for her from my side is day by day increasing, right now i am not settle. i think that she will not nikha with me, but not sure, if i will not nikah with her i lost most precious think in this world and hereafter and i cannot forgive myself, in these days tears coming out from my side for her every time. please advise me, and pray for me that Allah give her to my nikha in this world and hereafter. what should i do?
2) a ghair muqallid friend ask from me the reference of this hadith please give the reference of this hadith
?The Prophet sallallaahu alayhi wasallam has stated in a hadeeth that a person will be resurrected in the state that he died. And a person will die in the state that he lived.Hence we should endeavour to always remain occupied in doing good …actions so that our death and our resurrection occurs whilst doing good deeds.