She's a teenager and the whole world revolves around her, so being compassionate and understanding are not things she is capable of.

She's angry and grieving and she didn't get to day goodbye to her father, not to mention that she had just miscarried her own baby that she was starting to care about. She's looking for a place to put the blame and Jack is the easiest person to point the finger at. Now that she learned that he had something to drink, she has even more to use against him. While I don't agree with her, I know that I can't expect her to be resonable given the circumstances.