Yes, as a US citizen, you can file F4 visa for your sister. But this takes about 12 years to become current and so, given her age, [43 years, this may take too long. Therefore, I suggest that in addition to F4 visa, you should also consider other options for your her to get a visa in a much shorter period of time under which, she and her family can come to the US. You will need to consult in detail with an experienced lawyer about the various alternatives for her.
Answered on May 20th, 2013 at 8:20 PM