Will I be sinful, and will my deeds be displayed (to Allah), due to my estrangement from my friend and not knowing her whereabouts after my repentance and my desire to reconcile with her?

It is not permissible for Muslims to ostracize one another for more than three days due to a worldly problem. Since you have repented and tried to contact your sister but were unable, we advise you to go to her and reconcile. If that is not possible, and you are truly repentant and bear no malice, then we hope that Allah will forgive you.