Correcting K-2 Child's Surname??

[Samuel and Marvic 4]

Hi all, long time forum lurker, and this place has been a great source of information through my journey so far. I've ran into a rather big issue with my paperwork today, so I'm hoping someone can help me out here.

Last week, I received my NOA2 for my fiance in the Philippines. However, when we were collecting the documentation for the passports (something of a different issue altogether), we came to discover that her daughter's last name is actually listed on her birth certificate as her biological father's. The guy's been completely absent from her life most of the time, and I hadn't even realized when I filled out the initial forms that it was different from her mother's.

Who do I need to contact at this point now that the petition has been approved and is scheduled to move to NVC and out to Manila? I'm hearing different things like contacting the USCIS or waiting until the embassy receives it to contact and get it fixed; I just want to get this corrected if possible before she tries to go in for her medical and interview. PLEASE don't tell me that it's too late, my fiance is already freaking out about finding this, and the last thing she wants to do is delay the process or leave her daughter.

[Samuel and Marvic 4]

*bump*

Does anyone have any ideas as far as if I can get this resolved before she begins her medical process? We're kinda hung up right now because she has to to go get a yearbook for her passport ('valid ID'), but I'd like to get this resolved before they begin the medical processes within the next two weeks!

[Samuel and Marvic 4]

I noticed in the example Instructions for the assembly of the K-1 Visa this particular section:

If you have one or more children not listed on the visa petition, or a current pregnancy, or a prior undisclosed marriage even if the marriage has now been terminated, or are currently afflicted with a contagious or communicable disease of public health significance, you must be prepared to present a notarized letter from the petitioner stating he/she is aware of the discrepancies between the facts stated on the petition and your actual personal circumstances, and still wishes to proceed with the proposed marriage.

To be on the safe side, I think I'm going to identify this discrepancy and submit his; however, when it says "notarized letter from the petitioner," to clarify does that I mean I'll have to take my statement to a notary have it stamped and signed? Just want to make sure if I can get this taken care of properly so as not to incur the wrath of the delayed petitions...