Don't do it. She can't be all that nice if she is trying to get over on you. She won't even respect you afterwards . She consider it a weakness which she will keep trying to exploit.
I make it a policy not to do business with anyone in my congragtion. They all seem to think there is some kind of automatic discount they can claim.
And don't dicker! just say kindly with a smile on your face that you will not accept her propsal and that she should have a nice day.