Expediting NVC's review for additional docs

[SaiGrace]

This is for my mother's Green Card. I sent all the necessary documents needed before the interview in April 2017. NVC needed only one additional document and which was sent on June 17th, 2017. How long NVC will take to review? Since it is only one doc that needs a review, can I expedite the review process any way so her case is decisioned.

Thanks