Give her another deadline. Might as well make it a week or two after new yrs - so she can't use 'the holidays' as an excuse. Send her the 'bonus' deadline via certified mail if you can.
Go thru the stuff and see what could be donated (Goodwill, Salvation Army, churches, etc.) rather than pay to dispose.
See how much it is to rent a van for a day to dispose the stuff vs a disposal Co.
You could offer to take her stuff to an agreed location, for an agreed fee.
And, since she's rich AND you have her deposit - don't feel bad about any of it during or afterwards.
Block her calls and send her Emails to SPAM - but don't delete them for awhile, just in case.