The part where Georg, the counsellor, helps Tina to her first real breakthrough in the grief process. Tina's dialogue in that scene is heartbreaking.
Tina: The only thing I can't forgive her for is that she died. I just don't understand how she could do it. How the hell can she go and get hit by a car and die and leave me behind to take care of Mom and Dad and friends and life and missing her, missing her, I miss you, I miss you so god damned much!
Tina playing her violin for the first time after Cilla's death and in her mind hearing Cilla join in on her flute. When she stops playing she notices her father listening at the doorway, moved to tears.
"I'll never be able to hold you again, Cilla."
Some of the dreams Tina have after Cilla's death, particularly the ones where a dead Cilla crawls into bed with her and wants Tina to help her get warm again.
In the book Tina opens a spread in her diary and fills one page with Cilla's name and the other with "I miss you". In the movie she writes "I miss you" over and over again in a Word document.