The fact that everybody is still peeing in a litter box is a good thing, no matter whose box they use. It's ok to let the bengals sniff Nyah's room. We often recommend that before introductions are made, the resident cat(s) spend a few days in the new cat's room while the new cat gets used to the house. They have to acclimate to each other's distinctive aroma. There will probably be hierarchy issues that the cats need to work through and you'll need to keep a close eye on Nyah until she's big enough to fend for herself.
