I planned ahead two months in advance, but was faced with a myriad of delays (e.g. getting my fourth teaching waiver, the weeklong Islamic holiday of Eid al-Adha and the usual yearly mess ups by the school administration in getting a date or number wrong). Nothing new for me, this mess.
A few years ago I was facing the same problem as I am now, and immigration gave me two weeks "under consideration". Hopefully, they'll do it again if necessary.
Talk to the headman of her Issan village first. Buy him a crate of lao khao and he might be willing to let her go. Don't forget to pay the barfine for the entire period though!