Question Summary:
Can I renew my Nikah without the presence of the father?

Question Detail:

A Hanafi couple wish to renew their Nikah due to kufr utterance by the wife. 
Can this be done with 2 mature male Muslim witnesses present, as follows, without the presence of her father:
One party says: "Will you marry me?"
The other side replies: "I have accepted." 
Her father will not be present as she does not wish him to know what happened

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
 
A valid marriage takes place with exchanges to commit to marriage from both parties in the past or present tense. For example, the boy says, “I have married you” or “I am marrying you”. The girl responds by saying, “I have married you” or “I am marrying you”. These exchanges take place in the presence of two male Muslim witnesses who even understand that a marriage is being conducted.
In the enquired situation, the one party saying, “will you marry me” is a request to marry. It is not a commitment to marry. Such a statement falls short of fulfilling a fundamental condition for the validity of a marriage. [1] [2]
And Allah Ta’āla Knows Best
Abdullah ibn Mohammed Aijaz
Student Darul Iftaa
Baltimore, USA 
Checked and Approved by,
Mufti Ebrahim Desai.