Stories where a platonic relationship or encounter is a really important event

[Jade]

Looking for stories where a platonic relationship or platonic encounter is really important to someone's life. So not romance-centered, and I think I'd prefer stories where death or fatal illness isn't the main theme either, but the books can be witty, melancholic, thrilling...

[Gillian]

The Language of Flowers. Romance is important, but one of the most important relationships in the book is between the main character and her potential adoptive mother.

[...cats?]

Love & Saffron
The Reading List
Last Days of Summer

(all of these books include death/illness, but not as the primary theme)

[...cats?]

Social Creature
The Pallbearers Club
Great Expectations

[Pamela]

The First State of Being