Why Does My Kitten Sit On My Chest?

My two year old cat sits on my chest at night when I’m in bed. She doesn’t do it every single time, but there are times where she will not leave me alone and keeps pushing against me like she wants to climb up on the bed with me.

I know this is normal for cats because they want attention (especially kittens) but why does my cat act like that? Why does she sit on my chest if i can’t hold her or pet her? Is it ok for them to be cuddle buddies like that??