Transfer of property in co-applicant's name post relinquishment

Dear Sir, I along with my sister own a property in Noida extension which is under construction. Consequently we had availed a joint home loan for the said property. Now due to my sister's wedding, mutually agreed decision is to transfer property in my name (my sister to wilfully relinquish her right) and to ensure that the loan liability is entirely on me. Now, builder demands a NOC from lending bank. Bank in turn has asked me to apply for a takeover loan as we have to remove my sister's name from loan. Now, since property is in joint name, builder buyer agreement has both the names. Banks say that all parties to builder buyer agreement have to be borrowers under the loan, which in turn doesn't resolve my purpose as I want to take loan solely on myself and get a NOC issued and consequently transfer property in my name. Due to this I am not able to transfer property in my name. Family Issue: Sister's Marraige is in 2 weeks, her groom knows about the property. I am afraid I might face problems in future as my sister holds half the right as of now. I cannot trust her groom. I would request you to please guide me with a solution to this situation, wherein I can ensure that I obtain full rights of the property legally. Also, suggest If we can go on for an agreement, wherein I can include her groom to be a party to agreement, and obtain statements from them regarding full transfer of rights at the time of possession. Will a Power of Attorney work in this case? Or should i proceed to execute a MOU between me and my sister? Please come up with some solutions. Need urgent guidance. Quick Response would be much appreciated! Regards, Abhinav