I am guessing at the least, there is some sort of a strapless bra built into the front of it, here’s why:
–Her bosom doesn’t seem to shake or jiggle much during the video, and it doesn’t move much when she lifts her arms either. I mean look, she’s walking around and there’s no jiggle…yet her bosom doesn’t look small enough to not have jiggle. It defies physics, lol. No jiggle prolly means there’s a bra under there.
–The structure of the fabric means it would be stretchy or loose, and not well suited to holding on all by itself. It would fall down unless there is something underneath holding it up.
There’s really no way for a piece of fabric to stay wrapped around the body as well as her top does, without some sort of undergarment providing an underlying structure. It’s not an entire corset-type thing, like a longline bra, because the back is open; so that’s why I think it’s just a strapless bra of some sort. It just has a very narrow back section, so the connection point of the shawl-thingie keeps it covered.
Now, you and I can wrap a bathtowel around ourselves and tuck in an end…and it stays up. But that’s not how her top looks. There’s one little point in back where it’s hooked together, and it doesn’t look to me like it’s tight enough to stay up by itself (ie without an underlying structure of some kind).
I notice this stuff because I’ve been sewing for over 20 years. I’ve learned how to deconstruct ready-mades to come up with my own version. I am also a sort of hobbiest about medieval/renaissance clothing construction, which has all sorts of tricks for using shaped undergarments to make outer clothes achieve what looks impossible.
If I had a better figure, I would make something like this in a second.
EDIT: Think along the lines of those demi-bras that go into bathing suit tops. There is probably something like that underneath.