If she is receiving maternity benefit and you have already applied for children's allowance then that is the limit of what you will get. There are no dependent tax credits.
Is she going back to work when her maternity leave ends?
Otherwise you could apply for the medical card and family income supplement which is means tested.
after maternity leave is up she will be unpaid, maybe if she has enough stamps she might get something, but ultimately unless you earn pittance, you'll have to support her..