Verbal agreements in this instance mean absolutely Zero.
Your Mum's wishes are expressed in her will and should be honoured.
You have had some good advice in response to your thread, but you appear to be defending your Aunt going by your replies.
Bottom Line: IF YOU WANT YOUR CASH, ENGAGE A SOLICITOR NOW.
I'll see her Tuesday, try again and go from there.
Take your solicitor with you or someone who is a bit more assertive.