what do i do if my previous apartments sent me to collections claiming i owe them money i dont believe i owe them?

Upon moving out the landlord claimed i owed her money for a non-exsistant hole in the tile floor, the need to repaint the walls and a cleaning fee. When i asked for pictures of this hole she could not provide any. I dont smoke so why did she need to repaint the walls? and i spent 3 days cleaning so why the cleaning fee? And now her story has changed. The details collections gave me said I owed her money for new carpet but didnt mention the tile in the kitchen with "the hole". The wall repaint and cleaning fee still exsist. She said she needs new carpet because of my dog and bleach stains. Yes i did have a dog there but I put down a security deposit and a pet deposit both of which she kept upon my moving out, as well as the monthly pet fee i paid while living there. Did none of that money go towards fixing up the place. and my unit had no washer and dryer so i didnt have bleach in my apartment. The landlord was upgrading the complex, i feel she just wanted me to pay for the remodel.