1) builder buyer agreement has been executed by builder in favour of you and your wife .
2)your wife can execute an affidavit wherein she should mention that she has no right , title interest in the flat and has no objection to sale deed being executed in your favour by the builder
3) she should also intimate the bank to transfer the loan only in your name as she has relinquished her interests in the flat .
4) you should contact the builder regarding documentation to be executed so that sale deed is registered only in your name .
5) your wife should also in the consent terms undertake to execute all such documents in future as may be necessary for relinquishing her interests in the flat