Whoa! What did your cat do to vet? O.O
My chihuahua hates noise and if she can avoid that - she will do anything. Depending on her mood she plays with the kitten. My chihuahua is very calm type. Too calm. And because of that the weight just keeps growing. She probably has predisposition to obesity and her calm nature doesn't really help. Chihuahua don't usually weight 5.5 kilos.
So playing with kitten is a good exercise for her.
And this a photo of me and the kitten. I made photo with my phone, so sorry for bad quality. :/