I haven't been able to watch the video as i'm in work but my advice around strumming would be to listen carefully to the song (and obviously follow the instructions on the video) and then by a process of trial and error try to replicate the sound. I know my playing improved significantly as soon as i started to play along to my favorite tunes as well as using tab.
Hope this is useful - keep at it
It's downstrokes, like you said, but she is also playing the opening strings in between each chord. It's the last 8th note

1 and 2 and 3 and 4 AND 1 and 2...

on the AND, she hits the open strings. She isn't consistent though, especially when she starts talking.

But hey, life is easier when you're hot.