Dude, its either copyright or trademark you are talking about, and copyright is limited to artistic expressions that are in a fixed form. If anyone owns the copyright to your friend’s house it would be the original architect who fixed plans on paper. . But maybe you are talking about a photo or drawing she made of the house?
If not,
Perhaps your friend has some kind of contract wih Hallmark that works with a trademark, but it also could be an agreement outside of copyright/trademark laws. Just a contract between the two parties.
Speaking of this, many months ago and artist contacted me saying that she had made a drawing of my house and asked if I interested in buying it. I guessed from this that she was genning up business and that if I said yes I’m interested in that art piece, she would quickly do a drawing of it. Since I can draw my own house if I put my mind to it, I am not interested.