Not shown doesn't mean not happening. The party was trying actively to buy time for the soldiers to recover and ether rejoin the fight or get clear. the screen time and focus was on the hero though. The healers main job is healing, her focusing on the wounded makes total sense, yes it could have been shown, but your outrage is wild. At multiple points there is progress in their recovery before the charm spell, your just asuming a healer had no hand in that.
“Outrage”, not only are you writing for the author you’re writing for the poster. If it’s not shown, that’s bad storytelling because they took a clear amount of time to establish what her problem would be and we also know that in the story it’s important to the plan of our main character. You ARE assuming the healer had a hand in it because you’re making up stuff that isn’t present and that’s not good. When nothing is there nothing can be made of it, but the difference is that in my post I at least gave examples of what is shown, you are talking about what you think makes sense.
A basic aspect of writing is "incident and consequence”: there is something that happens (incident) and then something results from that (consequence) but the reason those words are used is because the nuance tends towards tension or conflict. In these chapters we were give incident but no consequence whatsoever. To illustrate, I can give you some examples of practically the same beats but actually showing consequence, all of them have the base incident of Sainte being given the lustful boost:
1. When the demons blow up the army the first time, they are hit with a huge area heal that surprises the hero. ‘Wow that was amazing! What did you do?!’ She turns to look at the Sainte, but the panel showing the Sainte from the hero’s perspective shows her on her hands and knees and shivering. Demons resurge and hit another blow up, Hero looks to Sainte, but they are now more collapsed and shivering harder. Succubus shows up and casts her lust buff and the fight comes out as the same.
In this case we can see how the lust is affecting the Sainte because from the hero’s perspective, she cast an unusually strong heal spell and is overcome by the exhaustion, but we know it’s actually the lust which “technically” made her stronger but the erotic effect is clear. Focus is still on hero; storybeats are effectively the same; four panels are used.
2. After the demons blow up the army, Hero says ‘Gather your strength! Fiore get them some help!’ she replies ‘Uh.. hn- Yes! Protect the wounded!’ Fight continues and then at one point we move to Sainte’s POV, she is healing the wounded soldiers one after another as her eyes twitch and she bites her lip, it’s clear the lust is taking effect but she seems to manage as she heals the last soldier in front of her. But then she turns around... there are DOZENS more. One falls and she heals on instinct but her knees wobble. Another reaches out to her and she heals but lets out a moan. Seeing that soldiers are being healed many heads turn and their weary battle-raveged hands and eyes reach out to her as the Sainte’s expression begins to turn somewhat feverish, and through the throng we see Ricola smiling. Cue her calling their attention and then going, ‘You’re still good to go right? Get it up!’ Story continues as written.
We get a small cutaway scene that shows the progressive effect of the magic, the willingness of Fiore to continue despite the effects, her reaction at being ‘overwhelmed’ and that Ricola is keeping an eye on her implying “things are going to plan”. Would take about 4-5 pages depending on the paneling/page choices.
3. Change practically from what is already written and shown except her expression/stability of body and replace a few characters to show that throughout the battle her condition is progressively becoming untenable in order to insinuate that she has to have been at least exerting herself somewhere, since the incident stated [random stats boost => become horny]. Notably: Ch24, pg16, bottom right panel, replace healer with fiore and change dialogue; Ch24, pg17, top panel, replace healer in smoke with fiore; Ch24, pg28, far left panel, and shiver lines/blush/flushed expression to Fiore, Ch24, pg29, top panel, match expression on Fiore from previous page; Ch24, pg38, top middle panel, add minor blush and slightly changed expression to Fiore; Ch24, pg39, middle panel, match expression from previous page add 1-2 more smal sweat beads to differentiate from others in panel; Same edit pg43.
If you actually look at these images and pages without seeing the way that the Sainte was looking/acting just prior to the fight, any reader would be unable to ascertain that she was under any sort of effect because of her infrequent appearance and completely matching the minor duress indications of the other supporting characters.
Not shown means not happening when there is no indication whatsoever, and she has NO indication. Plus in my edits I actually inserted Fiore firing off a healing spell i.e. showing that she could be understood to be back with the soldiers at any given point in the fight. If that was there you might have had a point, but sadly (Grunch).