Flash forward and I have since replaced the logic board and top case, as these seemed to be the top choices for replacements for spill damage. The new logic board didn't do squat to fix it, but with a new top case and the old board, I managed to get the machine to turn on once. After I tested that it was in working order, I shut it down and finished screwing everything back together. I tried it again, but it decided not to cooperate and not turn on yet again.
The macbook is getting power - the led from the power adapter is on and the battery now has a full charge as well. When it did turn on, the keyboard worked fine, and opening basic programs worked as well. Needless to say, I'm stumped and would like to get it back to her asap.
This long-winded explanation leads me to my question - does anyone know of any other parts that may have been damaged that could prevent the machine from starting up completely? Or would it be more beneficial to have her sell this one for parts and just get a new one? I was hoping I could get some suggestions here considering how uickly I got a response about the logic board model last time.