Hassan

I have filed petition for my sister, who is residing in Pakistan, in
1994 and it got approved but now I have found out that some how I did
not include her correct last name (her last name changed after
marriage in 1982). Currently prioroty date is 1991 for this category.
So it may take her another two to three years to come to U.S.
Can I apply for the name correction on her petition that was filed and
approved in 1994 at this time (after 9 years).
If yes, do I need a lawyer, if not, what form do I need to use.
I really appreciate any input.

Sincerely