I engaged to a religious girl but when I discussed with her some financial matters she felt that I am a miser and refused me.
I did not try to return to her considering this is the result of Istikhara.

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.

First of all know that the girl to whom you are engaged is alien to you.  So, it is unlawful for you to stay with her in seclusion or talk to her except for dire necessity.  So, we advise you to repent from everything you had committed that did not conform Shariah.

As for the question you asked, we believe that you should do your best to marry this girl since she is, as you mentioned, religious.  You could achieve this by correcting the conception she has of you.  You could use your mother and/or sisters for that aim.  Otherwise look for another girl for marriage and we hope Allah will make your things easy.

Allah knows best.