I just ruined the prettiest fabric

[rebeccas-sewing]

Cut the strips three inches. (When you're not sure what size to cut just take the finished size of the squares,in this case 2.5" finished and add 1/2" for the seam allowances.)

By the way, it'll be fine! Don't point it out to the recipient. She will never realize that you cut the fabric wrong. The old saying, "I didn't make a mistake, I meant for it to be that way" will save you lots of frustration when your plans don't always work out the way you intended.