My daughter (19) coughed up blood a few days ago. She's never done this before. It was around 4pm and she hadn't been coughing hardly at all. She coughed a couple of times in the kitchen and she spit in the trash can and there was a lot of bright red blood. She coughed again and more came out. After about 10 minutes there was no more blood. She said she felt fine. Why did this happen if she hasn't been coughing and she hasn't been sick? Her doctor said if it happened again to call. We go to CF clinic next week and we'll get more answers but it really scared us. Any advice?