My Layla does this too! But she uses cushions and pillows. When she was a baby she'd knead with her paws, but that has stopped now. She'll just stuff her face into the pillow and start sucking
I've noticed she seems to do it to calm down. When she gets really excited, she'll run around for a bit and then look for a pillow! She also likes to do it after eating meals... she'll come straight over to me if I'm on the couch and I'll lift her up and she'll start sucking on a throw cushion
I think it's just the cutest thing! She does it before bedtime too, if I let her on the bed while I'm reading. She snuggles up beside me and sucks on the corner of my pillow.