Agreed. You need to get to an attorney and see what other IP problems you have. You also need to see what IP opportunities you have. Perhaps you could interest Mattel in working with you rather than against you. Better to deal than to squeal. Better gain than pain.
And, Consider this - Why are you using a BARBIE doll and not some other doll? I think you know the answer and that is why you are here asking. If it is close enough you have to ask, it is way too close for comfort.