Belongings on Property after purchasing an owner occupied rental

[Sarah Black]

Ok this was not a traditional sale, we purchased a 3 unit rental property and now reside in one unit and kept on the tennants we acquired upon the sale of the property.

They had existing leases that were very brief to say the least. Also, one of the tenants was the MIL of the man we purchased the property from. This is where things become complicated, she previously used to occupy the unit we are in and had (per her) added several pieces to the exterior (giant urns, other yard pieces) and had lots of stuff in the basement/garage.

The previous owner left tons of other stuff behind and we have been working through cleaning it out and/or using what was useful. The hard part comes when the Tennant is claiming everything is hers. 

I haven't been able to find anything on the legality of this sort of situation, how do I know what is hers and what isn't? The basement/garage/ yard was not listed as part of her residence in either lease.

We obviously don't want to take any of her belongings but I also don't want to feel like I can't use something that is clearly a fixture in our owner occupied unit.