Reporting late fees to credit bureaus

I just spoke with an office manager about a bill for $12.81 from a visit back in March 2011 that I inadvertantly did not pay becaue I thought the bill had been taken care of by the insurance company, but am willing to pay. She is not willing to drop the late fee of $35 that was assessed because the bill was not paid in a timely fashion after several attempts to contact me by continuing to send a bill. Can or will this affect my credit if she reports it to the credit unions for failure to pay the late fee?