Dear Dark Kitty-
Since it sounds like you are the new owner, its sounds more like an adjustment period. My cats too peer into dark places for long periods of time. In fact I have one that rarely comes out from under the bed during the day.
I also have 4 cats too. Two of them are fairly active during the day roaming around my house, competeing for my lap, and generally making a nusance of themselves when I am working on my computer during the day at my job. Yeah, I work from home.
However, the other two loonys are my night kittys. My two Siamese are rarely seen during the day except as two lumps in the bed, or sleeping behind my storage boxes under my bed. But at night this is when the romping begins. They are up chasing eachother around the house until the wee hours of the morning.
Sometimes when I come in from my Graveyard Shift that I pull as an Armed Security Officer for DHS, (20:00 to 04:00). See I have an 8 to 4 job! Yeah! I will find my to Siamese Girls waiting for me at the front door. Its quite entertaining because the other two are Zonked Out on the Couch and at the top of the Cat Tree.
Don't be too worried about it. She is probably still a little sensitive from the surgery. She shoud come around in a few weeks. Try giving her a little Tuna in the mornings when you get up. I'll just bet you are going to have a new friend before long.
My guess is that she is a night Kitty like mine, and that is something that is just not going to change.
Good Luck!