Having been in a simmlar situation to your DD2 (but wasnt told i was bullying but told to suck it up and do what ever to fit in) and was blamed for being picked on.

Tomorrow i'd go and see the AP, and suggest that he needs to talk to your DD and about what HE said to her and she was being picked on by this other girl and perhaps remind him that SHE (mening your DD2) was already upset about the original incident and suggesting a child "die" from her "bullying" was beyond any thing he should have said as the implications of that would go alot further then his bloody office. you're doing a good job of helping your DD2 and his words may mean she's worried that she'll cop the blame if anything else happens eather at primary school or high school. if he brushes it off when the princeable gets back bring it up with him - perhaps get your DD2 to write down what happend and what was said and maybe request a meeting with the other girls mum to talk about whats been happening to see if you can sort it out with her DD in mind to?