Your sister is a vegetarian and not a vegan? which means she drinks milk and eats dairy products which have sources of saturated fats. Coconuts also contain saturated fats.
Remar is correct, if very little fats are being consumed, then the only conclusion really is a hyperactive Liver. If you look up "familial hypercholesterolemia" this will explain the problem. The Liver is a brilliant chemist that can make many substances for the body using available materials, one such substance being fat. Statins are very affective at lowering the Livers ability to make these Lipids, I'm living proof. My Cholesterol was very high, and even if I only lived on bread and water my cholesterol would have stayed very high. Statins reduced the cholesterol significantly and with the added medication of Ezetimibe, which slows fat absorption through the gut wall, my cholesterol is way below average now. I've been on these medications since the start of 2007 with no side effects which blood tests have continually confirmed. Familial hypercholesterolemia affects 1 in 500 people in many countries, so it isn't that uncommon.
This could be a genetic problem. Have they started her on meds?
Do you mean to say that no vegetarian should have high Cholesterol level unless he/she has a genetic problem?
For me it is in my genetics. My Triglycerides were over 2100 before starting on Tricor.
Ed34 and Chatty explain it well. I take Vytorin, which mixes drugs to control both ingested fats and cholesterol manufactured in the liver. I also take 2000 mg of Omega 3 oils to encourage the development of HDL (good) cholesterol. This mix has helped me greatly.