I have a Maine Coon Cat that likes to nibbles my knee when I am on the computer...?

I have a Maine Coon Cat who at times will go off by herself and act disinterested in human contact --but the minute I sit down to read the newspaper or type on the computer she runs over to me and meows incessantly and nibbles on my knee? WHY DOES SHE DO THAT? She doesn’t BITE me just nibbles and meows!