Tenant Privacy Concerns

[Abdul Tayyab]

First of all, it's my my fault for not following through properly. I'm reaching out to for any feedback or advice on how to move forward. I have a SFH with three unrelated tenants sharing Laundry and Kitchen.
I have a tenant (AB) that moved in after a current tenant (AA) recommended her own distant niece. After AB moved in she didn’t like the fact that AA comes into her space unannounced and just hangs out. AA doesn’t understand what the big deal is and continues to do so.  Now, AB would like me to build a wall with a door that will close off the area for her aunt to just come in whenever she pleases and is threatening to stop paying rent due to her privacy being violated. 
Does anyone think I need to build this wall or are there some other options I could look into?  Thank you.