Getting nervous

Hi Everyone~My Daughter has had Diabetes now for just about 2 years.  She is 10 years old and has just been absolutely terrific with everything.  Since she has been on Christmas vacation (she is back to school now) her blood sugars have been running high and even insulin doesn't really bring it down.  I am getting really nervous about it.  For example I went to school for lunch at 12:10 and her blood sugar was 240  I gave her 9 units.  She calls me at 2:15 telling me she doesn't feel good and took her blood sugar and it is 246...  Why????? I feel so lost for the first time (besides when she was first diagnosed).  I am scared that her body is rejecting insulin. Can this happen?? Has anyone else dealt with this issue? Please let me know!!!

Thank you all so much!