Part of the issue is that magic = sex is about as common as vampirism = sex
Here is how Willow and Tara get together in
Buffy the Vampire Slayer:
They've been hanging out doing magic spells together prior to this. But this scene is the "I trust you" scene, and the magic is meant to be more intense than their prior forays. (Also, they knew they weren't going to be depicting sex scenes between women, so while these actresses can hold hands and kiss, the magic rituals are meant to be stand-ins for off screen sex scenes.)
...and while dance needn't = sex, the implication is always just under the surface. Viewers are primed to take it that way. So, the choreographer would have to tread very carefully indeed to design a magical dance that doesn't read as entirely sensual. For instance, in the Sia music video above, it should be rather clear that the younger, smaller person is feral...and also dangerous in her own right. A natural interpretation of the relationship between the two characters might be father and daughter. Apparently, the story is meant to be that she's a werewolf! That part isn't obvious, though, so plenty of people took the video of an adult man dancing with a young girl as a portrayal of pedophilia. That may say more about the audience than the dance, but it was said.
I suppose it helps that Lúthien's magic puts people to sleep. So, there should be a heavy, weighty quality to her dance in Angband that is...quelling. That would put a damper on any tendency to view her dance as enticing.
I am not familiar with ballet, but I do know that there is a confrontation with a sorcerer at the end of
Swan Lake. So, I looked at a bunch of different versions of that to see how it was handled...and I am none the wiser. What is clear is who is in control - so Lúthien will be in control of those she is dancing around, whether that be in the initial enchantment of Beren or putting all the werewolves in Angband to sleep. BUT - controlling the wills of others in Tolkien's world is evil, and Lúthien wouldn't do that

So, she gently suggests they enjoy a nap

.