Landlord withholds utility bill from tenant until end of lease?

Landlord had water bill in her name. We agreed that every month or however often the water bill came in, the landlord would pay it up front and send us the bill to reimburse her immediately. After asking her multiple times throughout our 2 year lease to send the water bill as we do not want to pay it in bulk at the end, she fails to send us any of the bills. Now it is the end of our lease and the water bills are Outrageous! If we would have known the bills were that high, we would have been aware and conserved water to lower the bill. Due to the fact that the landlord withheld those bills (when that was not the oral agreement), we would not be in this situation and the bills would not be as high. Are we responsible for paying this amount? She wants to take it out of our deposit.. can she? Help!