If you have a registered will in your favour, a No Objection Certificate (NOC) from your sister is generally not required, especially if there are no disputes. While a release or relinquishment deed might be more appropriate than an NOC, its necessity depends on specific circumstances. Probate is typically not needed for a registered will unless the property is located in Mumbai, Kolkata, or Madras. If your sister does provide an NOC, she may need to appear in court to provide witness testimony.