stop where you are and go see an attorney. are you sure grandma needs I-601? your dad even though is a petitioner is not a qualifying relative for I-601 purposes. Possibly there could be a qualifying relative, but you need to meet with an attorney sooner rather than later
This is not legal advice and a client attorney relationship is not created. For a free consultation call (718)234-5588.
It depends when and how she entered the U.S., perhaps she is eligible for adjustment, and if so, she can file that now. If not, it will go to the National Visa Center and she will be scheduled for an interview abroad. If eligible, she may be able to file the I-601A provisional Waiver before she leaves the US.
The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.