Read the website or book "Five love languages".
It deals with how we as humans show our love in five ways, and prefer one over the others. The way we show love is our favorite to receive love.
Eg
Words of appreciation
Time spent together
Gift giving (even tiny items like a flower picked from the yard)
Doing thing for others- giving of self or taking care
Touch (hugs, arm touch, hand holding, sitting close while reading MMM, etc)
I bet your Mom is either a gift giver, or more likely a " do things for others" person.
So when you reject the time she took to put the box together, you are rejecting her offer of love.
The point is once you figure it out, you know if you can say:
" How wonderful of you to do this for me! I can hardly wait to go through it when I get home to see which pieces I can really use. Is it okay if I give some away if I can't use it myself?"
Or, if the primary language for your mom is gifts, just show lots of appreciation, take it away, donate secretly, and bring your mom small gifts when you come over. " I was thinking of you and wanted you to have this pretty rock I found on my walk yesterday..."