She doesn't look like she is very experienced. I doubt taking it back would help because I think she's probably done the best she can do. If it really bothers you, I would take it to another quilter to see if it can be repaired and chalk the cost up to "lesson learned."
I read something in a quilt magazine last night though that might help for the white thread. This quilter says she uses permanent markers to cover things like that. She says she has one in every color. You wouldn't do it large scale, of course, but it might help for little problems.