I'm sorry your sister lost her battle to the cancer.
The blocks are beautiful. I'd go with a deep rose/burgundy shade for sashing to make the blocks pop. Maybe a little darker than the applique on the 2nd row left block. Then maybe an outer border in a creamy background floral with several of the colors in the individual blocks and the same fabric for binding that you used for sashing.
Be sure to post a picture when you're done!