I warned my 4.5 year old in advance of the spider's fate, there's no way I could've just sprung that on her. So, her first reaction after we finished was to say she didn't like the book because Charlotte died. Clearly, she just needed time to mourn because the next day she wanted me to start reading it again.
What I didn't anticipate was her being put off the book at the start because of the threat to Wilbur's life. I think that was more difficult to deal with because there are multiple moments of threat and it's not like dying of old age. But once I reassured her that he would be ok, she was keen to continue.