why did May took her life?

From the text:

Dear August and June,

I'm sorry to leave you like this. I hate you being sad, but think how happy I'll be with April, Mama, Papa and Big Mama. Picture us up there together, and that will help some. I'm tired of carrying around the weight of the world. I'm just going to lay it down now. It's my time to die, and it's your time to live. Don't mess it up.

Love May

May kills herself Kevin.

may kills her self in the river and theres her note in page 210