Just to update you all ... this is what the manufacturer of Sophie said after I emailed them today:
>>>Yuk! I think that's the worst thing that has happened to Sophie so far...
Ok, she can't go in the steam steriliser, the rubber can't handle it. Don't immerse her as the squeaker goes.
Best bet is to wipe her down with a damp cloth and get all the much off, then spray Milton or other sterlising liquid onto a cloth and wipe over again. As long as she's not totally dunked in water the squeaker is ok, so wiping is best.
I hope you get her back to her former glory!!!<<<