Me too!
Surely the photoshoot was not for the underwear, why would she be wearing two and have mentioned putting a shirt on if that was the case? Make it make sense!
Edited to add:
On further investigation, someone asked her where the vest* was from and she tagged the company, who then retweeted her pic, so I think they're just trying to get publicity from a blue ticker wearing their stuff rather than it being a photoshoot actually for them.
*There's probably a fancier name for it, but it looks like a vest to me!