I'm thinking that if none of the above work, you could use tracing paper to trace the dotted design and flower onto it and then put it on a piece of white fabric and needle turn the edge following the outer dotted line. Sounds like a lot of work but your quilt is gorgeous and it just may be worth it. So hope that the vinegar works. Let us know for future reference.
Just to say, I was sanitizing 15 one-dollar bills to put into my great grandchildren's Valentines (doing it on my ironing board- not too bright) and the ink came off the bills onto my ironing board cover. I tell you! Who knew that the ink on our money can be wiped off???