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, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It is permissible for the man to marry a second wife even if he is unable to support both women without their help as long as they accept that, because financial support is a right for the wife and she can forfeit all or some of it. However, it is better for the one who is unable to provide support not to marry a second wife as we have pointed out previously in Fataawa 91737and 138664.
Accordingly, it is better to leave that woman alone and to try hard to sever all attachments to her. If you are not able to do so and your heart remains attached to her, then there is nothing wrong with marrying her if she accepts to forfeit all or some of her right to financial support.
As for the Prayer of Istikhaarah (i.e. seeking Allaah's Guidance), you should know that scholars hold different opinions regarding what one should expect after performing Istikhaarah: whether it's a feeling of assurance in the heart and finding the matter easy to undertake, or whether one should proceed to undertake the matter and not leave it unless Allaah, The Almighty, removes him from it? What we view is that one should proceed to undertake the matter after doing Istikhaarah and not leave the matter regarding which he performed Istikhaarah unless Allaah, The Almighty, turns him away from it.
Allaah Knows best.