I agree, take her to a vet if it's a chronic problem. The only danger I could see from this is that it might get infected.
On the other hand my kitten Zoe came to us with her bottom lip cut completely in half. It was so bad that it looked like her entire jaw had been chopped in half. The vet peeled her lip back and looked at it and said that it would heal and leave a little scar. He said she looked good, in spite of having a low grade fever and didn't even prescribe any medication for it. It has since healed up to where you can't even tell it was ever cut. Her bottom lip just looks slightly pulled back from her gums.