Habits for child
Habits such as nail biting, thumb sucking and hair twirling are irritating but not necessarily a sign of disturbance. The child derives pleasure from them and they become a habit. They may have been started in times of stress and continued because they provide comfort and pleasure. It is not worth making a fuss about them because you will then create tension which will need to be relieved by the habit! Most children outgrow these habits, others carry them through to adulthood. It is not worth worrying about.
Grinding of teeth during sleep is sometimes said to be caused by worms, but this is not the case, although the child may in fact have worms, since they are so common. Teeth grinding does no harm and will probably be outgrown. Some children pick their noses at night, causing them to bleed. You can of course tell her to stop, but it is unlikely to have any effect. Try-putting a little petroleum jelly around the nostril to keep the area soft so that it is less likely to bleed if she picks off a crust.