Doesn't seem to do much.

Makes sense. Her elemental was out of its, well, element. Next up: any water around to see what happens when a creature gets doused?

There isn't any nearby, but it's cloudy and could be induced to rain.

Not with this set of equipment. Anything in the clouds isn't currently liquid.

Either of the two larger water spirits can provide enough force to hold her bubble in its shape and in the air. If a regular-sized drop separates, has its shape maintained the same way, and several tons' worth of force continuously accelerate it toward a monster, how does the creature react? Better have it start from somewhere other than the floating sphere, in case anyone looks for where the gunshot crack came from.

That knocks it backwards hard; the fiery glowing briefly goes out, and it lashes out at random. The Elves press this apparent advantage, but they're still overmatched.

It didn't penetrate? Really should have; either the target is even tougher than it looks or it's the recently earned bad luck coming around already.

More of the same, then, with less spherical drops that might be more likely to break through its skin. This is easily repeatable; it can have one shot after another until she thinks of something else.

They're more denting the thing than penetrating it. Maybe it doesn't have anything that can be thought of as skin.

This would be easier if she could shoot it with more than one thing at a time.

But hitting it this hard is doing something; maybe if the next order is to just hold it down the people who were fighting it on purpose will get an opening.

They do manage to batter it pretty hard. It has serious and visible injuries, now, white-hot and not-exactly-bleeding out across the ground. 

And then it explodes into a fireball.

It's hard to tell from up here who's injured and who's dead after the explosion.

Doing the same to hold off the other creatures is probably the best move in any case. Whichever of the remaining monsters is outmatching its opponents by the most can have a bead of water pressing down with several tons behind it. (Seriously, how is this less damaging than swords. Something's up.)

The Elves are now wary about killing the things, and warily hold off when another one gets battered to the ground.

If there's an injured one, she might let this one up while she checks whether their not-exactly-blood is water-based. Attacking it from the inside can only be better.

Yes, whatever it is is water-like in the relevant sense.

In that case, the overworked water spirit gets ordered to seize the liquid dripping out of the monster, and the adjacent liquid inside the monster, and tear it in every direction possible.

While the monster's opponents are as far away as they're likely to get, just in case having all its probably-not-exactly-blood-vessels ruptured simultaneously both works and is explosively fatal.

It does! Boom! And now the other ones are fleeing. 

The Elves come back to gather their wounded and dead.

To show up now, or to wait until they get back to their camp....

Well, at least one of them is going to be able to connect her voice with the mysteriously interfered-with monsters. Is the one who had to be warned to stop running ahead of his army still alive?

He is. He's helping retrieve his injured fellows.

Then there's no advantage to waiting.

She lands as silently as possible, breaking the connection whenever one of them might have noticed her, and makes sure there's nothing out of the ordinary visible. Then the temperature disguise can come down.

Hello, she attempts. I have a message for Fëanáro. Are you with him?

They start.

"You're speaking to him," the one who'd run out in front says warily.

HELLO FROM THE OTHER SIDE, she doesn't say.  YOUR COUSINS WHO YOU LEFT TO DIE  can stay likewise unclarified. It'd be genealogically incorrect anyway.

It's from some relatives of yours. "We are crossing the Helcaraxë. No one has died yet, which means it's not too late yet for you to set this right."

"I see," he says. "Tell them not to do that. Once we've won the war we will go break everyone out of Valinor and since they are so determined to be a liability they shall have to wait until then." 

Amber sticks with the telepathy. This isn't the time for testing fluency in a new language, even if she did mostly understand that.

You are a lot more confident in being able to win alone than they are with both groups. Determination I'll grant, they have a lot of that. Was that why you stranded them, because you thought they'd be a liability?

I stranded them because they have a number of members who openly declared that they desired to reach this continent only so they could undermine me by any means available to them, and because they do not acknowledge me as having any authority over them, and because a significant share of my resources were constantly deployed, whenever we were in close proximity, on ensuring that no two idiots started a fistfight that ended in a civil war. And because my half-brother either decided to claim the title of True High King of the Noldor at the moment when it was most necessary we come to an agreement on transportation, or else has so little control over his people that he was taken by surprise when they all spontaneously chose that moment to do it. And because they already delayed me by several months for reasons that had no prospect of changing and time was and remains of the essence. 

Tell them to go back to Valinor and let us win the war and then we will come and rescue them. 

They know that's what you expected them to do and they're already not doing it. I'll tell them what you said, but don't expect it to change anyone's mind. The other option being to stay on a continent run by the kind of gods that throw around Doom without aiming very carefully.

You went to some extreme lengths to get those ships in the first place; you could have guessed the others might take extreme risks to get across without them.

We don't have the means to help them. We lit all the ships on fire.