What is the best way to deal with a hoarder? What is the best way to be sure that my aunt is paying her bills?

Hoarding is a serious mental issue as well as physical health issue. Adult services with Department of Children and Families can help. It is not safe either because of accidents because of problems getting through the mess, or feces from animals, domestic or wild - one house I helped with in getting it suitable for in home services, was full of mouse and rat feces, endangering the health of the elderlies. In addition to, or another route to take if there is medical poa - - is to inform the persons's doctor of the situation and enlist help and references through them..

It kind of depends on whether they asked for help or not. If they have asked for help, if you have the money hire a professional organizer and work with them. If not, and the situation is bad, talk with them and explain how the public health dept. could be called and that you might want to clean it up together. Even if you keep most of it, maybe rent a storage unit to store it. Then you can sneak it away or forget to pay for it. I know this sounds cruel, but my aunt was this way and part of it was to due to Alzheimer's and the hoarding can make a home very unsafe and hard for the emergency workers to get in if they need to. As for her bills, set them up to draft out of her bank account. That is what I did. Hope this might help a liitle.

Totally agree with GrandpaHiker above. As the 'caretaker' of a person who hoards we can easily become co-dependent enablers while attempting to help. And ruin our own lives in the process. A person has to 'own' their problem before they can be 'helped'. They have to WANT help. Period.
Here is a cautionary tale in our own family. My husband and his ex wife, mother of my stepchildren who are all grown, divorced over 22 years ago. My oldest stepdaughter, married with three little kids, has been to her home on several jaunts in the past umpteen years, rented a dumpster, thrown stuff out, enlisted the help of her sister, cleaned up her mother's home, etc. It would get bad again; she'd go back again. Her mom, who was left in excellent financial shape by my husband and who also had an advanced degree and a very good, supposedly tenured teaching job, just over time decided she didn't like her job and quit doing it for the most part. She also evidently didn't like making her house payment either, or paying other bills, as we have gotten calls over the years about trying to locate her and collect. She was finally let go with a settlement with no recourse and a year's heads up from her job a few years ago. She was going on 60. Her dogs left feces on the floor that never were cleaned up, her car was in disrepair and was no reliable because she neglected it, her home was full of stuff and falling down around her and was foreclosed on, meanwhile, more and more stuff piled up. Her utilities were cut off. More and more stuff.
My stepdaughter 'ordered' her to leave her home (which the sheriff was coming to evict her from anyway) and move to another state to live with her and her family. Her mother ignored her orders until the last minute and resisted any help, became mad when she was told what she 'had' to do, until my stepdaughter pushed her enough that she did finally go to U Haul It to pick up a rental truck to bring some stuff down. At the rental place, she called her daughter saying she didn't have money for the truck so her daughter put the charge on her card. She was mad about having to do that. The mom showed up. Moved in. Said she had no money at all. No health insurance. Crying because her stuff was gone.
It turned out, after a year's worth of prodding her, pushing her, yelling at her, begging her to discuss her financial state that she disclosed that she had more money than anyone knew in a 401K. Turns out she also has a teacher's pension, part of my husband's pension and finally got a job. In that year, she did nothing to lift a finger at her daughter's home (who works, has a husband and 3 young children) - no laundry, no meals cooked, nothing. Now she has finally moved out - and cashing in her 401-K to help purchase a new convertible! She has wrought a path of distraction in this young family, her daughter, who was trying to 'help' her and her husband have been at odds (no privacy at all for them or their family, etc) and she has been a financial burden as well.
Many of this woman's shall we say 'idiosyncrasies' had everything to do with why she and my husband could not be married. She never was and never will be a grown up. She is a constant and eternal victim. I am positive she will hoard again. I hope her kids have learned a lesson.
Most of us can see the train wreck coming and want to spare those we care about the misery of the pain of that train wreck. But we see it as if it were 'us' and not 'them'. The bonus in all of this too is that, having failed at achieving the change she wanted to see in her mother and mad about all of her in-vain efforts, there has also been, I believe, a growing resentment toward my husband and me because my stepdaughter doesn't feel that she should have been the one burdened by all of this (resents their divorce even though it was so long ago). In my opinion, she was never asked for the help in the first place. No lesson was ever learned by a person who has never had to face consequences in her life; someone has always bailed her out. And her issues continue to split and harm seemingly every one but really, herself.

My MIL is a hoarder. In my experience there is not much you can do unless the hoarder realizes she has a problem & asks for help. When my FIL was still alive every Sunday morning while my MIL was at church he would take a pickup load of junk & trash to the dump. During the week MIL would accumulate more trash & junk. She never realized what was happening. Since my FIL passed away, my MIL's house looks & smells like a dump inside. MY wife & I got caught hauling off a load of wet cardboard, old carpet, bags of trash, etc. & my MIL hit the ceiling. Very few people visit her because of the smell & there is no where to sit & little space to stand.
So my suggestion is that you stop trying to "fix her" unless she asks for help. Trying to fix her will just cause frustration on your part & anger towards you on her part. As with my MIL, we have come to grips with the fact we can not fix the situation. Once my MIL gets to the point that she has to go to assisted living we will have a big roll-back dumpster delivered to her house & hire men with shovels to clean out the house.
I am reminded of the prayer ...... Dear God, please help me to understand that in life that are some things I can change & some things I can not change. Please give me the wisdom to know the difference.