Sometimes people make if difficulty for us not to "go down to their level". Sounds like she probably pushed your button one time too many during the conversation. Just take this as a learning experience and move forward being the bigger person in the future.
As others have suggested, give future customers a written estimate after you have seen the quilt. If quoting prices by phone, state your rate of $.01 and note specialty quilts are higher. Good luck with your new venture!