If the quilt has sashing you can save and use the block by adding fabric of a complementary color and squaring it up.

The person who made the block may have put all of her heart & soul into it and did the absolute best she can do. It might be crushing for her to have her block redone.

I say wait a bit and see how other blocks turn out. They can't all be perfect across the project, so likely there will be a few that need some attention (not just hers). Then you can honestly say that just like with any quilt ever made (by you or anyone else), sometimes a little adjustment is necessary to make everything fit properly. You don't have to completely redo it, though; I think just enough to make it work.

Definately the best advise you got - also remind the ladies that "many hands make light work" and ask them to sign up to help set up / break down. If they commit to a particular time / day call the day before with a gentle reminder so that they don't "forget" they signed up.

Maybe save all the wonky blocks and do something creative with the backing?

This is probably the course I would take to. Maybe the person who made it won't notice and if she does well, you can explain it was that or leave it out all together because it just wouldn't fit correctly. Either way someones feelings may get hurt and she may feel her efforts were un-appreciated.

I've had similar issue and you cannot repair, replace or leave out without hurting her feelings. She obviously wanted to participate or would not have volunteered. My opinion from experience is leave it as is. The other option is possibly saying you had 1 or 2 blocks too many and pieced them into the back so everyone's was used then add her's in back, make a second one for back if you need to. Or could her's be utilized as a label?

I like the idea of using hers for a label! That way it actually has pride of place without the problems of having to fit it in with everything else.

I agree!!! If you wanted a perfect quilt then you should have made it yourself. Put her block in the center surrounded by all the perfect squares.
First it will make her feel special and will let her know her efforts are appreciated (which they should be).
Second remember God allowed "special" people to be made imperfect and He still loves them just as much as perfect people. If God wanted perfection He could have had it.
Third as with any quilt there will always be something someone else doesn't like or would change, but someones effort is what makes it special and loved, not its perfectness.
Keep it as is and make it special!

Using it as part of a label sounds like a good idea. Are these experienced quilters? If some of them aren't, then maybe a separate demonstration of the correct way to make the block step by step is the way to go. This could be a general demo not singling any one person out.

mltquilt

Sorry, I don't agree that you should take it apart and re-do it. Unless you made it expressly clear in the beginning that you would accept only perfect blocks for your quilt, you should use what is offered and realize that not everyone can do all things to perfection. A gift is more precious if sacrifices were made to create it. The recipient will know that someone's heart was in the right place ~ even if her stitches weren't.