Yea if you have only had Gizmo for a month then he will do better than if you have had him for a year. He will still miss her but he knows you and the kitty too so he is used to yall as well so it wont be bad. Just give him TONS of loving and play with him as much as you can to let him know you are his mommy. I went on vacation and was unable to take Reeses with me so I left him with my parents who have a weenie dog and my jack russell 9who was attached to the weenie dog so lives with them instead of me and so my fiance got me Reeses cause I have always wanted a yorkie but we werent sure how Ginger-jackrussell would do with a new baby in house. lol) Anyways...my parents said after I left Reeses just laid on my bed and was sad acting all day and didnt eat his dinner..well the next morning he didnt eat but by that afternoon he was playin with the other dogs and ate that night and was totally fine. Of course he was SOOOOO excited to see me when I got back...but since my parents loved on him lots and he had a companion to play with when they couldnt..he did fine. Im sure your lil Gizmo will do great as well!!