I don't know if what I say will help, but please, PLEASE find a way to get your hubby's aunt "Evicted" from your brain. Her thoughts and opinions right now don't matter. YOU matter. You and how you feel about youself. Allowing her to take up space in your brain in a negative manner is going to do nothing towards helping you move forward.
In watching & helping my husband through two separate addictions, he and I both learned that the proof is in the putting so to speak. Your actions will speak volumes more than vicious rumors by someone who can't or doesn't want to understand what you are going through.
I think your aunt has lost trust in you and is dealing with it by saying bad things about you to her daughters. Is this the right thing to do? Absolutely not, but not everyone is able to deal with broken trust in a positive manner.
Regaining lost trust takes time. Right now, you need to focus on you- getting yourself better, healthy and clean. It sounds like that's what you are doing, so please do not allow this woman to throw negativity into your healing process. Like I said, it will only make your journey that much harder.
You admitted you have a problem and are taking steps to correct it, right? So what I can say to you is hold your head high and keep moving up that hill because once you reach the top things are going to be beautiful.
Good luck sweetie, and take care of you.