http://www.catbehaviorassociates.com/pica/It is quite common in Early Generation cats, I would guess it is due to the stress such cats are under in the domestic environment.
Was she hand reared? When was she weaned?
You are right to be very concerned as eating non-edible material can result in intestinal blockages and even death if left untreated.
Vet ASAP I would suggest to exclude any chance of her being seriously ill.
I would suggest a good cat behaviourist for the pica, as it is a very complicated issue and a potentially deadly one and is IMO outwith the scope of the forum.
I would choose a behaviourist who is used to dealing with and understands wild cat hybrids.