Degus teeth are too long.!!!!

Our family has 4 degus. We love them dearly, but I sure wish I had done more research before bringing them home. One of our females got into a fight with another and we found her bleeding terribly in the cage. She had a lot of blood coming from the mouth area and out of her nose. There was so much blood that it took us a couple of days to figure out what exactly happened. In the meantime we took her out of the cage and put her into a different cage with fresh water and food and a warm towel for comfort. Of course we watched to see what would happen. She seems to be missing her front lips. OUCH!! Her teeth still looked strange to me but I was not sure . We had to feed her water from a syringe and cook little pieces of sweet potato and other stuff to get her to eat. She slowly got better over a few days . But her teeth look exceptionally long and she is rubbing the fur off from around her eyes. WHATS GOING ON? We have started to give her water again and softer food but she is thin and does not look very good. My daughter put an apple branch in the cage and she seems to be chewing it,but what about those teeth??? Is there anything that I can do to help shorten them. Is it possible to gently file them. I absolutely can not take her to the vet. We just do not have the $$. I thought degus were like gerbils and I had those growing up. I feel awful for the little sweetie but I just do not know whaT TO DO. Can anyone help???