So they gave her an extension until date of passport expiring (Jan), but now she has a new passport. What steps does she need to do to get it extended until contract ends (Apr)? Show up with all paperwork again? Will have to pay again? Or possibly to make extension from now (Dec) to (Dec) even though work permit ends in (Apr)? What's the best avenue here...

Edited December 6, 201510 yr by happysanook

Yes !

Show up with all the paperwork and make a new application for an extension of stay. The fee will have to be paid.

She will need to do a new extension application. The fee of 1900 baht will need be paid.

She will need a letter from her embassy to have the stamps transferred to her new passport before they do the extension.