I like the sashing, and black would be my first choice, followed by red. The main thing is for her to feel good about the decision. Kudos to you for getting her so involved so early!

I like the quilt with sashing. I would let her decide which color she likes best. Each color gives it a different look. I like the way the yellow softens the look of the blocks while red and black really makes them pop. The blue gives it a totally different look. Any way you do it will be beautiful.

This was my choice too!!

Sashing
 

I did one of these and just made the center with no sashing and then added borders.

My choices in order of first to last would be black, red, none.

I love it with black around it, have you ever done wonky using all 12 blocks. I think this will really be cute with wonky setting and a crazy quilt border.
Michelle in Omaha

I like the black. Finished size is usually decided how wide you make the sashing/borders.
If you want to use 1 cut of fabric for the backing (42/44inches) keep this in mind when
you fiqure your sashings/borders. Nice to see young quilters. :-)

Ditto! I like both the red and the black...The red really makes it cheery, but the black makes it look more classy and arty. .

The sashing looks great.

My vote is:

#1 - black sashing - it makes the blocks pop!
#2 - no sashing
#3 - red sashing

Great quilt! Very vibrant and lively.