snephenie...I see you're in California too. I think you're on the right track. Talk to your apartment manager, and maybe introduce yourself to Elaine. See how that feels. If you still feel that she's been abandoned or is a danger to someone else, you could call social services (check your phone book). I believe you can tip them off anonymously.
I hope her son was just tired from moving and just made things sound worse than they really are.