Love the quilt. Those will be a really nice bridesmaid gift.
I'll tell you how I square up my quilts. I have to disclose that I am not a porfessional quilter, I only quilt for fun, so here goes.
I trim the extra batting and backing off even with the top. Then I line up my quilt on my cutting mat and try to square it up with the lines on the mat. I use my 3.5" x 24" ruler, for the sides and top, and my 6.5" square, for the corners, with my rotary cutter to trim off the excess pieces that don't line up. I make it as simple as I can for me.
Have fun.