What legally can I do to get these possessions back?

My mother passed away about 3 months ago and left her estate to my brother and me. I am the executor of her estate and my brother is schizophrenic. Unfortunately my mother left nothing for her expenses, her house is underwater and I have paid for everything. At this point, I am hoping to recoup at least some of my expenditures in the upcoming estate sale. My problem is that I have an aunt, Mom’s sister, who has property of my mother’s but does not feel like she “owes” the estate anything. Some property my mom loaned her other property the aunt took when helping clean out the estate and said she would pay me for, but has not yet. Unfortunately although I know Mom kept some records of what she took to the cabin it’s not all recorded and this aunt does not want me to go to the cabin and has politely kept me away. This aunt financially helped my mother when she was alive but there was never any formal or informal agreement that she would be paid back or given any of these possessions. In short I am financially strained by my mother’s estate, my aunt (who owns a multimillion dollar company) won’t give me what is owed the estate and is just ignoring my requests. I really need them back before the upcoming estate sale but have not heard back from the aunt. Any suggestions would be greatly appreciated.