This would not be an example of external conflict because external conflict is the struggle occurring with the characters mind. In this case it would not be an external conflict.
An internal conflict is something within the characters mind, so the person above is wrong. An external conflict is an outside force which poses as a problem for the main character(s). So, in the case the dagger is the external conflict, because it causes her death.
Because ‘Sarah and her sisters has gone’ doesn’t sound right, ‘Sarah and her sisters has been’ also sounds wrong and ‘Sarah and her sisters have been’ doesn’t really make sense
