I think the issue is that while the money is held in trust, that her money and anyone else in the minority has paid, have had their funds used to pay bills in full.
That means that there are likely no monies held to return.
The lease would set out how estimated and actual expenses are reconciled ( usually) and therefore that is a matter for determination which is binding on the freeholder and their successor in title.
By establishing actual expenses and enforcing the terms of the lease the next freeholder will be paying out money.
In the case of the administrator as I have told many over the years write to the mortgagee and they generally pay up.
Based on the information posted, I offer my thoughts.Any action you then take is your liability. While commending individual effort, there is no substitute for a thorough review of documents and facts by paid for professional advisers. More ramblings atleaseholdpropertymanager.blogspot.com