My landlord did the same to us. When I moved in into a sharing apartment, he almost kept a track of when I would return from the office and as soon as I reach, he would barge out of the main door and remind me about the rent, though my payment due date was 2-3 days ahead. I spoke to my roomies about this behavior and they told me that he had always been like this and we shouldn't be bothered it. So, even though he reminded me in the next coming months, we would say, 'ok, will pay it'. It bothered me in the first few months, but later I started ignoring it.
But, if this bothers you, you can start doing one of the following.
Put a reminder two days before the due date and when you meet her, say in a joking way, 'Lady, I have put a reminder to pay you the tent. See, I am so responsible'. Ensure to show her the reminder.
Or some other time, tell her how grateful you are that you have such a wonderful landlady who reminds you always. Also, tell her that half of the burden is removed from your shoulders.
The intention is to inform her that you remember before she reminds you. And also to maintain the rapport and yet be jovial without her getting defensive.
Or, just ignore her. Though you are paying the rent, she is still the queen of that house. She might be trying to exercise her rights or she might have had tenants who delayed the payment. We don't have to know. But, whatever you do, don't offend her.