The agency can't force you or the helper to continue the contract and can't keep the passport (it is illegal). I heard some people settled everything with the helper in front of an officer of labour department (e.g. salary, air-ticket, acknowl.edgement, etc). Try to call labour if they can provide any assistance. Regarding to the passport, your helper can report to the police and they will go the acency with her to get it back.