Question about cats grooming themselves?

Just keep an eye on her to make sure she's not irritating her parts excessively or showing signs that something is indeed wrong. Cats (and other animals) can develop obsessive-compulsive behavior. She may feel there is a hairball in there that won't come out and she's trying to "encourage" it along. My little female swallowed one of my long hairs (I try to keep the stuff swept up but one will sometimes escape and she'll step on it and lick it up during her bath) and it got tangled up in her poo so she was having a hard time passing it--acted like she'd like to scoot across the floor (although she didn't). I noticed this long hair sticking out of her butt, grabbed a tissue and pulled gently on it which seemed to get the bulk moving again.

I would ask your vet about it. Of course, they'll probably want to do bloodwork to be sure what the problem is. It could just be that she's not as good at grooming herself now that she is old, and just never gives up trying to make her coat perfect.