Immigrant Visa stamping in US - is it possible.

[mrlsthrm]

Hi,
I got a notification from NVC that all documentation necessary has been received for my petition for my Mom's immigrant visa.
My Mom is in the US for the past 4 months on a visitor's visa. This visa was issued way before I applied for her immigrant visa.
A priority date has been assigned and the letter says they will notify us about the interview date in a US consulate or Embassy.
Since she is already here can she get a immigrant visa stamping here? How can I go about to make this happen?
Thanks