It's looking like the medical person who comes in during the evening to assist the folks down the hall has a heavy gait. The lighting in the hall is motion sensitive so the lights go on high when someone walks through. When he walks by my mom's door, he casts a shadow on the floor and under the door. Easily visible from inside the apartment. The doors are designed to be self closing in case of fire. They close and latch on their own. They also rattle a bit because weather strip or cushions would interfere with the closing.
These details correlate with the description she has provided me in describing the 'harassment'. Plus the guy who lives down the hall gives out a creepy vibe.
I deduced this with one observation of the camera feed. I told my mom but she doesn't believe me. My brother also has doubts. Frankly, I am little disappointed, too. I was hoping to throw somebody off the balcony.