Assuming she's not hungry or needs to go out to hit the potty or something, she probably just wants extra love and attention from you today. Spend some time playing with her and talking to her, then try to interest her in one of her toys.
she/he is vocalizing. why don't you stop talking. its the same thing. the safest animals are the ones that evolved to be more vocal.. humans, bird, cats, dogs. your cat feels safe or threatened. check it.
Stand next to her and look at her in the eyes then ask what? Follow her until she knows you want to help and shows you what is wrong. You can also check her paws to make sure there is nothing like a small rock or pebble stuck in there and hurting her.