WOW! Lovely fabric, the floral is stunning.
several suggestions.
Is there a "natural" block in the fabric that you can cut without losing too much detail? a 12" or 16" or 25" or whatever? Cut there & then alternate with 4 blocks that total that square, made up of your coordinating fabric.
Fussy cut the floral & border them with your coordinating fabric. 1 border or 2, bringing them to all the same dimension.
Use all the flowers. They are stunning, and even tho sis loves irises, they go so well together, will add much interest in the quilt. :-)
Use the floral as your center panel, just quilting around each element. Make the border sampler blocks, a variety of dif blocks that you enjoy making, or want to try.
If that is too much work, narrow inner border, chinese coins, then wider outer border, all out of your coordinates, still with the floral as your panel.
...(keep me in mind for your leftovers, love love love that floral, me green with envy!)