At that level, she is very close to the danger zone - where her risk for life-threatening clotting issues increase (heart attack, stroke, pulmonary embolism, etc.). It may be worth exploring other options once her platelets are lowered but for now, my opinion (and I'm not a medical provider or an expert by any means) is that she start on the Hydroxyurea. Her doctor will carefully monitor her platelet levels and any side effects and will be able to adjust her dosage as needed. Best of luck to you and your Mom!