ok, here's her quilt:
http://www.quiltingboard.com/t-44929-2.htm#1025584
Are you making the same quilt? So you want it a square tree block?
Have you made your 9 patch blocks yet?
What size are those UNFINISHED?
Because that's what you have to match size-wise.
Adjusting the tree block is a lot easier.
You can see from her in-construction pictures that her tree and trunk were surrounded by larger pieces of the background.