How do I defend myself against my neighbor constantly calling the Humane Society on me?

My neighbor and I do not get along. She called the humane society on me last year claiming animal cruelty and saying I leave my dogs outside for hours while I'm at work, I don't give them water or shelter, I have an excessive amount of feces in my yard and they are outside for extended amounts of time during heavy rain and snow. All of which was unfounded. However, I got another lovely note on my door from the humane society saying they stopped by to investigate an animal cruelty allegation. AGAIN! I cant even fathom what she has made up this time. I haven't heard back from the officer. My dogs are never left outside while I work, thats insane! I dont leave them out during heavy rain or snow bc they have to come back in my house that they would get filthy, DUH! They have plenty of water inside and out and there isnt poop in the yard. I have 3 dogs so after 2 days of pooping in the same area I guess it may appear to be alot. But thats as far as it goes. I scoop every other day. Shes just mad because the other day after I worked 9 hours straight with no break (no, the dogs were not in their crates the whole time, my daughter comes home from school after 4 hours) anywho, I get outta my car and without even shutting the door, i turn around and there is my neighbors girlfriend asking if she can talk to me. I say sure but I have no idea who you are, bc I didnt. She claimed to live next door, I assumed she was the new GF, but hadn't seen her before that day, she made a comment about my side door. She requested that I scrub it clean because when she sits at her table and looks outside, she sees my "nasty door". She doesnt want to look at it, its grouse. I very sarcastically asked if she was serious. She said yes, I said I'll see what i can do, rolled my eyes and walked away. Just being honest. My yard is fenced to include my side door which my dogs jump on when its time to come in. Mind you, it rained for 3 days straight so it was quite a muddy door. Agreed it was dirty, but im not scrubbing it to appease my nosey non-neighbor. If all you have to view is MY side door, and thats the best view you got, i suggest changing windows. What can I do to defend myself to the investigators? Its embarrassing to have animal control pull up to your house and leave you notes while your not home every time the neighbor gets mad. Can I file charges against her for harassment? or some form of slander? I'm not moving bc I own my house, so does she. Do I file against my neighbor or her girlfriend?