I would consider give full-dose anticoagulation because she has high risks of recurrence DVT. The risks are Age>50 and unprovoked isolated distal DVT. The flight to Korea impose risk of VTE during the flight although the duration is 4-5 hours (moderately long).
The choice of full dose anticoagulation eg. Warfarin preceded by LMWH, apixaban, dabigatran, endoxaban and rivaroxaban.
I will also recommended wearing elastic stockings,exercise every 2 hours, stay hydrated, avoid coffee and alcohol, quit smoking and follow up venous ultrasound to minor progression of thrombosis.