What is each saying about the other?
To take this any further the differing opinions of the dry cleaner and the manufacturer have to be resolved. The only way to do this is to send the dress to an expert for an analysis of the fabric and he dyes used in the dress. A fabric expert will produce a report and you can then take an informed decision as to what to do from there.
You're welcome. Happy to discuss further. Don't forget to leave a positive rating so that I am credited for my time.