Window leaks from hole in bottom of frame
Gutters would help a lot. I thought I saw water on the inside on the video. At the bottom of the window there should be 2 or more small weep slots / holes these allow the water that gets in the tray to drain out. I believe these are full of debris and probably plugged. If you open the window look outside at the bottom of the frame you should spot the weep holes or drain slots. now look inside at the same location they are probably full. A shop vacuum may help clean out the area but a small rag and a tooth pick can clear them. If you have horizontal lap siding it would be easy to take a piece of flashing and make a diverter slipping a few inches of flashing under the lowest overlap and fold it out so it creates a makeshift gutter and reduces the amount of water dripping into the window. other types of siding would be a touch harder to not look like a "back country red neck repair". Even a bead or RTV / silicone calking above the window 1' on 1 side in a straight line to just above the window may divert enough so it wont flow into the house once the weep holes are cleared. I would clear the holes it may take 20-30 minutes but this small fix could possibly solve your problem until it needs to be cleaned again. Good luck.