You shouldn't fake your own death.
Mary is in an online relationship with Tim, and is growing bored with it.
Mary wants to break up with Tim.
Mary is honest with Tim that the relationship isn't working out and breaks up with him.
Mary pretends she has cancer and makes Tim think she has died.
Tim is sad, but moves on and finds a new girlfriend.
Tim is very distraught, and spends months in a depression.