My yorkie was about 7 months when we brought her home. We have an almost 18 yr old cat and 1 1/2 yr old yellow lab. I was worried about how they would all get along. When we got the lab (at 8 wks) the cat tolerated her but once she got a little bigger the cat decided it was time to retire upstairs. LOL we have a baby gate at the bottom that the cat can get through and every now and then she'll come all the way down but usually is happy to hang out a few steps up.
Charlotte spends a lot of time upstairs with the cat, while we're gone during the day and evenings with me playing. She loves the cat and tries to play but mostly gets the cold shoulder. I think she respects her elder but still tries to get her to play. They both sleep on the bed during the day, sometimes fairly close to one another. I'm sure it's adorable to see....I only see the body indents on the pillows. LOL