I need to find that book!!

I was watching videos on the internet when I came across the following description;

"I was reading a book where she has three boxes in her closet, and when he asks, she says they're ex-boxes, where she keeps everything that's left over from her ex-boyfriends. But then he realizes she only has two ex-boyfriends.

My world fell apart when she showed him what was inside the third box."

I can't find the name of the book, if anyone knows, please tell me and explain what was in the box, I would be very grateful!!