Cuddles the friendly cat!?

My brother and his family are away on holidays right now so my Dad and I are looking after their two cats and my nieces hamster. They have one cat Cuddles who is about 18 years old an usually not a very friendly cat, in all the years I have only pet her once and when I did she gave a great growl. She really only likes my sister-in-law. Since they have been on holidays she has been meeting me at the door, rubbing up against my legs and actually letting me pet her. I'm amazed, she's acting like a normal cat! I guess when your favourite person is away you have to make do with second best!