Poppy gets spayed tomorrow!! I am soooo worried about her

She weighs under 4lb, she is as tiny as can be and i am just so so so so so worried about her
Has anyone had their baby spayed when they have been to tiny? She is running around all happy and she has no idea... i feel so crule!
Ugh i dont really know what to do with myself i am just so so so worried sob sob!!
Please can i have a little reasurance from u lot as i am worried i am gonna lose her!!!