Of all the body parts your dog rubs on the carpet when company is present, her nose is among the least offensive. Your pooch may start out rubbing her nose and end up in a full body wiggle and roll, ecstatic groans and all, leaving you wondering what she's doing.
If your dog tends to start the nose-to-the-carpet bit just after she eats, it might be brought on by an instinct buried deep within her. Rolling and rubbing after eating is natural wolf behavior. In the wild, a wolf will rub on the remains of prey he's just killed and feasted on, possibly to savor his victory. In the not-so-wilds of your home, your domestic dog may feel instinctively prompted to roll after a good meal and rather than serving as an act of triumph, it's probably become a habit, like when you stretch before getting up from the table after a big dinner.
Your dog's sense of smell is so much more sensitive than yours, she may smell something on your carpet that attracts her. It could be almost anything, from a smell that was tracked in on someone's shoes from outdoors or the lingering odor of perfume or room deodorizer. Your dog could be rubbing her nose on the carpet to fully enjoy an aroma that smells good to her and she might end up rolling her entire body in an attempt to smell like it herself.
It's possible that the reason your dog is rubbing her nose and sides of her face on the carpet -- and maybe anything else she can reach -- is that it itches. If your dog has an allergic reaction to something she's breathed in or eaten, it can cause her nose and eye area to itch. Without fingers to scratch herself, the next best option is to rub against something to relieve the discomfort.
Just to be Safe
When your dog starts rubbing her nose on the carpet, it's better to err on the safe side. Make an appointment with her vet for a checkup just to rule out an allergy or other condition that could be causing itching. It may end up being entirely behavioral, but if it is medically related, at least the vet can prescribe treatment which will alleviate any discomfort your pup is going through.