I am a property manager, my tips:
Have her request a copy of her rental agreement if she can not find her copy.
Search the state laws concerning notice and allowed alterations.
Make sure they have her current contact info and write a letter requesting they contact a certain roommate for all repairs (I see one tenant take the mail regularly and fail to mention to others notices)
You might not be allowed to change the locks or add a chain with out the property owners permission (check that lease copy and your states law)
Once you know your states law, write the landlord a letter with a copy of the state law and send certified to the property managements office with a request stating how you want to receive notice of non emergency repairs (note if they only have to give you 24 hours notice and you request they mail the notice, you will get it after they have come in)
Make that counter report at the local police, you might need that if you get a big ppv bill (or long distance if you have a land line)
Good luck (look for a better place and get that nanny cam just in case too) Personally, I HATE anytime we have to go in to an apartment that is not totally vacant!