I guess so, though there's not much she can do with just a crown.
Well, she could attempt to crush his head with it. I was going by
this pic where it looks like it's covering his face, though in op's pic it's on top of his head.
Jinora was at the spirit world at the time, and her spirit was separated from her body. Unalaq or Korra can't or at least haven't shown to be able to destroy a human whose both body and soul exist at the same place at once.
True, that's never technically been shown onscreen. But I think it could be done because of other similar things that are shown.
1. There is the
villain of the
canonical video game, whom Korra destroyed with spiritbending. Problem is the game leaves it kind've ambiguous as to whether he had his body while in the spirit world or not. He said he meditated into the SW centuries past, so he should be a spirit. However, he can still bend while in the world, which the show made clear shouldn't be possible if you're just a spirit. He also said that he was trapped in the world because the portals were closed, which shouldn't have been a problem for him if he had just meditated inside, so he could have just woken up in the physical world. He also never confirms that he had died sometime in the past (the wiki even says that he was exiled into the spirit world, not died.) It could be a Sokka situation where his physical body came into the world during one of the solstices.
2. There's the moment in the season 3 premier where Korra spiritbended the vines that had surrounded a building, making them retreat. True, the vines grew back a minute later, but that was likely due to their connection to the spirit world and the fact that Unavaatu at his full power was the one that created them. As shown when Kuvira's forces were cutting and gathering the vines in the swamp, their outsides are physically just normal vines, which means that Korra was able to bypass their durability with spiritbending and affect their normal insides. Similarly, in "Beyond the Wilds", Korra used energybending, which is very similar to spiritbending, to make the vine pods open up to release their captives and permanently retreat.
3. Jinora can meditate to sense people's spiritual energy that are nearby. Toph and Korra can touch spirit vines to lock onto a person's spiritual presence to find where they are. There is a
firebending technique that lets the user sense chi paths in a person's body, sense if their body is corrupted by darkness, and even
heal damage to the soul (check the abilities section). Since all these techniques of the other three elements bypass the body, it stands to reason that the waterbending version can to.
4. Going back to energybending being similar to spiritbending, the creators stated that the red and blue energies that covered Aang and Ozai's bodies when Aang engaged in energybending was their
souls flipping inside-out.
Sorry about the wall of text; I've actually been thinking about this topic for a while.