Do you have ONE pet and leave it alone? Hows that workout?

I have another question about my cat, so I have been thinking that since things are starting to open up, I will be going back to work soon. However, I am concerned about leaving my kitten whos about 2 months old home for about 9 hours. And NO I do not want to get another cat at this moment. I am afraid she may get depressed and lonely because she is so attached to me now I think. I mean at night I leave in my living room to sleep and sleep in my room and she does fine, I hear no crying, etc. Yet, I do not think she plays like cats usually do at night because I have come out of my room a couple of times and she just sits on the sofa with her eyes open. During the day time she sleeps and wants to be with me. Any insight? Will my cat be okay while I am at work?