Okay, approaching from the other direction.

We've been brainstorming, essentially, ways in which we would use Parian's power to fight an opponent like Behemoth.

What if we disregard the power entirely and just look at what Parian herself would do in that situation?

Her character: she lacks confidence, she feels isolated between the cape scene and normal life, and she's very much uncomfortable being centre-stage. I imagine she'd step up against Behemoth only out of (real or imagined) peer pressure - she doesn't see herself as a hero, she doesn't want to be a cape, she just wants to keep her head down, make things she enjoys making, and not get herself and her family caught up in all the cape bullshit that's flying around. Really, she'd be first in line to disregard her powers as all but useless and just head for the shelters or evacuation, but she's put herself out in the open and she basically has to either make an appearance or be forever remembered as that one cape who turned tail and abandoned everyone. Or at least that's how I imagine the process goes in her head.

So she makes her appearance, parading her giant animal cloth-golems onto the battlefield and tackling Behemoth. Of course, the constructs last even less time than they did against Leviathan, since Behemoth can just incinerate them as soon as they cross into range and they won't hold her power too long once they're on fire. So now she's stepped onto the stage, she's put herself out there, and it's basically for nothing anyway because Behemoth is brushing her parade aside and trashing her city and killing everyone and she can't do anything about it because her power just isn't enough and her dolls just aren't strong enough...

Two ways she goes. She either hides herself down and wraps herself up and tries to disappear, or she steps up. She takes the second option, starts casting around for something she can do to slow down the monster destroying the city and killing everyone in it. As a traditional mind bullets telekinetic, she can't make a dent - her power fizzles out if she tries to handle anything weighing more than a few pounds, she just can't exert the level of pinpoint force necessary to make Behemoth even notice. She can manipulate needle and thread with her tk, use that to fashion constructs from porous materials, and when she pours her tk in to try to lift them those constructs can contain her power as it fizzles out from too much weight, letting it build up on itself as she keeps trying to lift, and eventually she can use it as a crude hydraulic system to manipulate the constructs as giant marionettes. But those cloth marionettes are nothing to Behemoth in a straight up fight.

What she can do, though, is build herself a top-notch hot air balloon impression. She can fill the battlefield with hundreds of chinese lantern style tk balloons, run strings back to the ground from them, and effectively neutralise Behemoth's lightning. She can use her assembly-line tk to create inflated fabric dummies of people, run them through the battlefield to distract Behemoth, buying people time. She can't get herself (or anything she can really move properly) within a Behemoth's kill radius - maybe waterlogged fabric could resist being incinerated for a bit, but generally the more resistant it is, the harder it is for her to move - but she can do a good impression of disinformation and battlefield movement. If her creatures can trade blows with Leviathan, they can certainly carry a whole bunch of people, letting her also mount logistic and rescue operations.

Actually, I'm going to go off on a tangent here, as an idea's just occurred to me. What if she could create vacuums? Her power, when it fizzles out, tries to act on all the little things around. She moves her constructs by filling them with telekinetic pressure, and pushing that pressure in specific directions. If she just pushed 'out', could she create a vacuum around her by pushing everything out to the edge of her power?

And now that I've said that, I find I've pretty well lost my momentum on my original swing at things. So I'll leave this for now, maybe come back and expand later. Anyone reckon this rambling might contain the buried seed of anything?