I come in peace, I mean no harm unless you're allied with Melkor, I am from another Creation and want to stop Melkor, I would swear it but I am not a type of being that can meaningfully swear the same way elves and orcs can.

Well. Being hostile probably won't save them anyway. They communicate their greetings and gratitude. 

She asks about what has happened recently, because as a visitor she is thoroughly deprived of all the history of this world. And relates the story of the two (separate) hosts of Noldorin elves that are crossing from Valinor to fight Melkor as well. One has already arrived and is getting established, one is still travelling.

If someone will swear to her that this walled city opposes Melkor, she will be extremely glad to beef up their fortifications a bit, and perhaps more aid when she knows them a bit better.

They are happy to swear that. These are the Falas, and Ulmo protects them so her aid is perhaps more needed elsewhere. They've already met the first host of Elves, one of their princes rode here with cavalry and helped break the siege on Brithombar.

"Strengthening walls does not take too much time, but I would certainly appreciate it if you tell me of places that may need my help more urgently."

As far as they know the only people with walls to strengthen are them and Doriath, and Doriath is probably managing though now that it's clear they'll send messengers.

That's good. But reinforcing the walls is not really difficult to her, even impressive walls like these can still be improved, surely?

They would be grateful for her aid and improvements. Doriath probably wouldn't be, they don't have stone walls and it wouldn't fit their aesthetic.

Then she'll help where she's wanted and not where she's not.

She could strengthen the existing walls without changing their shape at all, or discuss siegeworks with someone and work out ways in which it would be desirable to extend them. The first thing is, obviously, much faster, and she rather likes the sentiment 'If it isn't broken, don't fix it' at least in some circumstances.

Yeah, they're pretty content with their walls under the circumstances, stronger but not more complicated seems the way to go. If that's all right?

Perfectly fine. She approaches the walls a little closer and evaluates how they were built and maintained.

Carelessly; they were clearly trying very hard but didn't know what they were doing.

She keeps up a running mental lecture on how-to-make-wall as she goes through, for anyone who's interested enough to listen.

It's not bad work, exactly, but not starting right has done this and that and the other thing... Without terrakinesis they'd have to tear the whole thing down, clear it, and start over. Cracks caused by water faults can be closed up, the foundation properly sunk in, access tunnels reinforced, unseen faults in the bricks or the ground accounted for, proper drainage installed, places where the walls have sunk shored up, the cracking mortar between bricks replaced by a much more weather-resistant sort of substance... She finds it very relaxing. It takes almost a full day.

"Thank you for the opportunity to do something constructive."

"Thank you for helping. We've been under siege for years, it's been desperate."

"Wars that last for years are outside of my experience. I don't know what is needed during them. In my home though, among others like me, there are lines you do not cross or you. Lines like destroying continents and torture and starting wars. Melkor has done all that and probably more. How else can I help oppose him?"

"...that's really hard to answer. Go fight him? We're not - we wouldn't stand a chance, but perhaps something like you would..."

"I plan to periodically harass him but I believe a direct assault without assistance is unlikely to succeed. I am not a Vala, the battle is not fair. So what I want is backup and to be a force multiplier without that making things worse. Would Doriath be offended if you told me how to visit them and introduce myself?"

"Probably not - afraid, maybe, but not offended - " and they point her towards Doriath.

And she flies there, stopping well outside what is probably-theirs.