Hi Rickman, hope things are slightly better. Regarding the lumps in the ABs, did they ask you to keep them in the fridge? some need to be kept cool, it should say something in the bottle.
I'm of the opinion of keeping her home, you may ask the teacher to send the homework if any to keep her updated.
I hope things get better very soon, and get some probiotics ready, she will need them to help her digestion after the ABs. As for the food, let her choose whatever she wants to eat (I suspect she would not feel very attracted by the foods that are going to be heavy for his tummy so, even if it's just bread, as long as she feels like eating them she will be fine)