That request isn't about your ex, it is about your daughter. I would help her to make the quilt and do the very best job that I could so she can be proud of the gift she is giving.
I admit that I don't have the experience of having an ex to give me empathy for your situation however the best thing I have ever seen concerning step family issues is Jada Pinkett Smith. I once heard her speaking about building a relationship with the first wife. She took the position that it is important to honor the first wife because she is the mother of Will's oldest child and that ultimately the happiness of everyone depends on the adults all having a congenial relationship that supports the kids.
I am sure that it is tough but do this for your daughter, now and in the future.