gee, if you've been tight friends forever just say outright you didnt hear any mention of size and only made it the size it turned out due to the size of the blocks and finish fabric supplied, and you added some fabric to it to boot. (and really, if you were just working with what was supplied it came out the way it came out! My MIL sewed for people, they took terrible advantage of her, she was a wonderful seamstress. They would expect her to buy sewing thread, embroydery thread, and extra fabric to do their requests - and they seldom paid her.)
let her know you'll help enlarge it. If you try to just ignore this you'll end up really feeling bad at yourself for not being honest. a size difference in a quilt is not the end of the world and can be fixed. sharet