Most commonly, trauma to the nose triggers a nosebleed. Trauma to the outside of the nose, such as a blow to the face, or trauma inside the nose, such as nose picking or repeated irritation from a cold, can cause a nosebleed. So if she's exposed to colder climate then maybe that's what's causing her nosebleeds.
Less commonly, an underlying disease process, such as an inability of the blood to clot, may contribute to the bleeding. Inability of the blood to clot is most often due to blood-thinning drugs such as warfarin (Coumadin) or aspirin. Liver disease can also interfere with blood clotting. Abnormal blood vessels or cancers in the nose are rare causes of nosebleeds. High blood pressure may contribute to bleeding but is almost never the only reason for a nosebleed. So if your really concerned about your friend you should tell her to go see a doctor to get some blood test and get checked out.
Less commonly, an underlying disease process, such as an inability of the blood to clot, may contribute to the bleeding. Inability of the blood to clot is most often due to blood-thinning drugs such as warfarin (Coumadin) or aspirin. Liver disease can also interfere with blood clotting. Abnormal blood vessels or cancers in the nose are rare causes of nosebleeds. High blood pressure may contribute to bleeding but is almost never the only reason for a nosebleed. So if your really concerned about your friend you should tell her to go see a doctor to get some blood test and get checked out.