Ive been experimenting with this tension for some time now, still cant get it right :/
Trying to convey tension is always difficult... A few thoughts that could be implemented ....
1. Tighter shots. Your actors are lost in such an expansive background. Move closer so your characters take up more on screen real estate. At 33 seconds Anna is barely visible.
2. Perspective. Using the 33 second shot for example, Anna could have stood closer to the foreground had she moved screen right. This should have kept the perception of distance between her and Lorie while making Anna easier to see.
3. Movement. When your actors aren't moving, the camera should be. Trucking right a bit at 33 seconds, or around Lori at 38 seconds would have added tension (especially had Lori's shot been tighter) As well as dollying in towards Anna at 53 seconds... you dollied away from her, which reduced tension.
4. Trimming. From 19 seconds to the minute 4 second mark each of the scenes could have been trimmed shorter to keep the energy up from one scene to the next, rather than trying to use long pauses to create tension.
Overall I thought your short was fantastic, it seriously left me wanting to see your next video. Keep in mind my suggestions are just that, suggestions... they're not intended to take away from your work at all, just observations from the comfort of my chair.