I decided to tackle the same song while back, took me a few days to nail it! I searched all over the web site the best way to play bouncing disco octaves but in the end came up with my own way.
Easiest method at first was the low note with the thumb, followed by middle, index. If we number the fingers starting with the thumb at 0, it goes:
0 2-1, 0 2-1...
However you don't get a good attack from the thumb stroke. It looks like that girl plays it with two fingers only, which involves a lot off string skipping. Either:
1 1-2, 1 1-2...
Or:
1 2-1, 1 2-1...
I play it this way, which is apparently uncommon yet feels most natural to me since all the fingers roll off each other:
1 3-2, 1 3-2
And the variation:
1 3-2, 1 3, 1 3-2, 1 3...