It's great that she doesn't have worms, since, as you know, this would be a symtom. Dragging her bottom on the carpet could also indicate that she needs to have her anal glands expressed. I would recommend taking her in to her Vet for an exam.
Why does a cat need its anal glands expressed? I mean what causes this need, she is awfully young, or does that matter? She won't even be a year old until next month.