When and how to intervene in tenant disagreement/fights?

[Tammy Richards]

Well, I've owned my 4 unit for all of 12 days and got my first tenant call loaded with drama.  The building is a low income rental for families, 3 bedroom units, 3 of the 4 units are section 8.  When I first met 1st floor tenant prior to the purchase of the building, she complained about the noise made by the 2nd floor tenants, and told me she was looking to move out.  The 2nd floor tenants make references to the nasty 1st floor tenant.  Both pay their rent on time, according to prior landlord.  

So today, the first floor tenant calls me.  She's upset that the 2nd floor tenants apparently tossed the wreath she put on the door into the street, and tossed a rug she had in the hallway into the street (they share an entrance way).  She then goes on to complain about how noisy and disrespectful they are.  I  figured I needed to stay out of the drama - and I told her that if the tenants were breaking the lease, I could do something, but that they needed to handle disagreements among themselves.  If they were disposing of her property, she did have the option of calling the police.  I also let her know that I knew she was unhappy months ago, and that if she wanted to move, she was on a month to month lease and that was an option for her to move, and that I was open to helping her by releasing her security deposit earlier if she needed cash to move.  During the conversation, she said she'd call the police, but that I'd get in trouble because there's an ordinance that landlords need to keep their buildings from being disorderly (I've since looked into this, I'm not too worried).

Throughout I was calm, respectful and polite - and I think she sensed that so I was able to calm the drama a bit - but honestly, I don't like this tenant.  When she moved in under the old owner, she got in saying she had a 3 BR voucher, but then only had a 2 BR voucher, so she pays less rent than anyone else in the building.  She's taken over the one parking spot, and has a boyfriend who has mysterious friends from Massachusetts.  I can give her 30 days notice - she's on month to month - but wanted to give her the option to make that decision.  

Should I intervene more/get involved?  I am interested in why the 2nd floor tenants removed the wreath/rug... should I call them?  Do I need more explicit leases about who can store stuff in the common hallway?  Do I call the police and warn them of the drama?  Other ideas, thoughts?

Thanks!