“千人同心，则得千人之力；万人异心，则无一人之用（出自《淮南子·兵略训》）。”这蕴含

Dear Aunt Chen,
My cousin is the ___1___ age as me. She’s really nice, and we ___2__ on well, but she always borrows my things. Last week, she borrowed my math book and didn’t ___3___ it. So I couldn’t do my homework. I don’t want to have a ___4___ with her, because she’s my best friend. I don’t know what to do. Could you please give me some ____5___?
Yours,
Michael