If it's teeth mine liked hard foods to gnaw on such as bread sticks.
Could it be that when her day pack was eaten she was going through a GS and you go used to her having a larger appetite? When appetite returns to normal after a GS it can be a bit of a surprise just how little they eat in comparison.
Congrats on your new LO
Perhaps your DD needs some extra attention, no necessarily focused around the food issue but just in general. Hard with a NB to care for, she maybe needs some extra snuggles.
I wouldn't make too big a deal about her eating, just keep offering the normal healthy foods at her regular times and let her get back into the swing of things when she's ready. I have not BTDT but I imagine now is a time when she could make food a big issue if you respond to her non-eating, it's one of the few aspects of a toddlers life they have control of.