you need to have following and you will be pretty much good to go
her medical records
affidavit from your grandmother that she wants to meet you
her birth certificate or anything that shows her identity
your parents birth certificates, or marriage certificate
you need to show proof that shows your relationship with your grandmother such as your birth certificate.(your birth certificate shows your parents names, and if your parents birth certificate or marriage certificate shows your grandmothers name you good to go,
send copies of your passport, driver license, and copies of work authorization card.
good luck