All Kinds of Model Trains Equipment

Soo we adopted a cat which is 1yr old and its a female indoor trained cat ..so it does everything a trained should do..shes a very calm cat..however we;ve had her less than a month already and whenver she comes on the leahter sofa to lie down and we stoke her she scratches it accidentaly apparently because she is happy and she isnt doing it on purpose..however since we first brough her home shes found a perfect scratching place the door mat and thats the only place she will scratch on..however we've let her to sleep in the lounge tonight because she will not leave us alone at night meowing for someone to open the door for her..so my worry is that she might ruin the sofa while sleeping through the night or scratch it..but im not to sure as shes already got the door mat as a scratching place she always uses..

any help will be appreciated.