Chatting? You chat with a blow up doll?

Its not cheating unless you lie about it, but then its only lying.

There is no emotional 'relationship' between the guy and the doll (unless he is insane.)

There is little chance that the doll will ask the man to give up his girlfriend or wife.

Point is, a person (the man) is not involved with another person. Its just a doll. What he does in the privacy of his home with a doll or with his own hand is his business. A woman who is so insecure that she calls that 'cheating' is a bit of a control freak. IMHO.

It is cheating, not the same as with another person, but it is a form of cheating.