Pica in toddlers

ne
My 19 month old likes eating paper products, I usually get her to spit out, but she doesn't stop doing it. I thought that's what babies do and they would stop but it's still happening. I've booked an appointment with the doctor. Does anyone know why she does this? Is she lacking nutrients? I provide her a balance meal, and give her healthy snacks between meal times. Any advice will be appreciated, thank you.