grey territorial on couch, help!

Her former "mommy" has been very sick and in hospitals for the past 4 months, and doesn't expect to fully recover. Her and her husband decided the best thing to do was to find her a good home where she would get the attention she was used to. (very hard decision for them) I didn't ask her specifically about the couch thing, from the little time I could speak with her on the phone, she was used to being in the same room with them only on her portable play perch and was not allowed to be on the couch. I'm thinking for now it's prob best to avoid the couch although she truly enjoyed the affection of the good head scratchings. I have to wonder if the couch felt like some kind of nesting place for her because of her sudden defensive behavior when there too long. Other than that....she is an extremely well adjusted, outgoing, not shy and very talkative all day to anyone!