Maybe she senses that you are preparing to go away, and she's "acting out". It could be that this is stressful for her, and she's taking it out on Samantha and Giz, don't you think?? My dad's cat, who adopted them and was an outside cat for most of his life, is like that. If he gets upset or feels that there is something going on in the house (like when my dad in and out of the hospital for his cancer surgery), Squeaks would be ok with my mom and dad, but he would pick on our other cat, Lucy. He was relentless, and he knew that Lucy hated him, and will get riled up over anything that he does. It's his way of letting my mom and dad know that he's not happy with the state of the home.