Question about duplex tenant issues

[Jordan Quinn]

We have a tenant that has rented from us for several years and we have never had any issues with her...other than her having issues with all of her neighbors. Around 4 months ago a new tenant moved into the other side of the duplex she is at and now we have had nothing but problems. New tenant immediately moved in girlfriend and 6 kids when it is only supposed to be him with one older daughter. Long term tenant on other side was complaining of excessive water running all through the night, noise, fighting, water being messed with to burn her while in shower. I've done a couple inspections on the new tenant to see what is going on. The unauthorized tenants have moved out after we sent a notice. Long-term tenant called again and said the water was being messed with and she was burned again. Not sure what to do at this point. I've documented everything but I don't feel like I have enough proof to legally do anything. Long term tenant said she has now had a heart attack from all the stress and is threatening to sue us if we don't get rid of the other tenants. 

[Greg Scott]

Id offer to let your old tenant out of her lease, no penalty.  Otherwise, offer to install a shower mixer valve which will prevent scalding.

You cannot remove the new tenants unless they are violating the lease.