Your cat is not alone in her favorite pastime. A lot of cats sleep most of the day, averaging 15 hours a day. Most of their awake hours are between dusk and dawn. That means when you are awake and ready to go, your cat will be hunkering down to get some shuteye.
Cats, by nature, are hunters. That means that they need bursts of energy to go after their prey. After those bursts, they need to recoup the energy that they used with a nap.
Cats are famous for their naps. They'll take a few 15-30 minute naps a few times a day. These naps are light, and they are able to spring into action at the drop of a hat. I don't know many people that are able to do that. It's one of the things that I find most impressive about cats.
I wish that I could be more like my cats!