She says her name is Mary

[Mayhem]

OK

I haven't been able to find anything on the property before the house was built

Ok With out giving the location might be a a standstill.

 

[Kairos]

She hasn't moved anything before, the only real pattern in behavior I've noticed is that she shows up more often when someone's upset. I'll try asking her the next time I see her

You describe a human spirit. Just ask her In the name of God, can I help you? Keep reminding her she is dead.

If she moves very heavy objects, and gets very angry at the above statement, then "she" is not a she at all and you need help.