All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, we ask Allaah to guide you and us to His right Path and enable you and us to perform acts of obedience to Him and refrain from His prohibitions.
You should be very grateful to Allaah that this girl cut the relationship with you, as it is not permissible for a Muslim to establish a relationship with a marriageable woman. Therefore, you should repent and not look for any means to re-establish the relationship with her, as this is seeking something which is forbidden and this is not permissible.
For more benefit on the ruling on an affectionate relationship between a man and a marriageable woman, please refer to Fatwa 81356.
Furthermore, it is not permissible for you to supplicate to Allaah to re-establish your relationship with this girl because this is supplicating to facilitate a sin and it is confirmed that the Prophet said: "The supplication of a person is answered as long as he/she does not supplicate for a sin, or for the cutting of relations with kinship." [Muslim]
Your statement "I did not perform Istikhaarah because I am scared of His Decision" is very dangerous; this is not a polite statement to say regarding Allaah and you should repent for it. If you do not want the Choice or the Decision of Allaah for you, would you then want Him to leave you to be in charge of your affairs? Whoever Allaah leaves in charge of his our affairs, will be doomed. It is for this reason that the Prophet used to supplicate: "Allaahumma rahmataka arjoo fala takilnee ila nafsi tarfata 'ayyn, wa aslih li sha'ni kullahu, la ilaaha illa ant."
‘O Allaah, it is Your Mercy that I hope for, so do not leave me in charge of my affairs even for a blink of an eye and rectify for me all of my affairs. None has the right to be worshipped except You." [Ahmad and Abu Daawood]
Finally, it should be noted that it is permissible in Islam for a Muslim to marry a woman from the people of the book provided she is chaste. However, there are many disadvantages for such marriage; therefore a Muslim should avoid marrying women from the people of the book as much as he can.
For more benefit on these disadvantages, please refer to Fataawa 84724 and 89418.