Like ==when and why she contracted then exactly? If her disappearance was connected to Touka and Nemu, then did she kept in touch with them after she left hospital? Did her becoming meguca was connected to it? I was assuming it was, but then why Iroha wouldn't be involved in it. If she didn't heal Ui first, it'd make sense how all of them wished to be healed by Kyuubey and after learning truth about witches, they could try to work together against Kyuubey, but explanation how Touka learned the truth also wasn't like I was imagining it at all (and honestly sounded like a bad joke).
So it seems like Touka and Nemu wished to be healed to leave hospital shortly after Ui was discharged, but then it leaves the question how Ui was exactly involved in Magius thing. Did they basically dragged her into it without her knowledge and why? There's just much things that doesn't seem to make sense when you try to put it all together in any sensible timeline.
Given how uwasa are created, I'm not sure that Touka and Nemu actually wished to be cured - depending on their disease, merely becoming magical girls may have been enough to save them. And even if not, Touka's enough of a schemer that she could probably have cooked up a wish that would involve curing them as a side effect.
But even if, my issue with the pebble thing is that it assumes that somehow Kyuubey would never appear before Iroha, someone with terminally ill sister and is desperate to heal her, to offer them contract as well as apparently before Iroha healed Ui Kyuubey never appeared before Ui as well? That Kyuubey that manages to find and stalk girls with even the most superficial problems? And if that wasn't hard enough to swallow, he also didn't appear before Touka and Nemu and let them die every time, until Iroha healed Ui? Sorry, but ignoring flimsy rules how time traveling and creating universes in Madoka works, I really can't buy that Kyuubey of all people aliens, passed on 4 potential megucas.
The issue there is we don't know how Kyubey detects or prioritizes candidates, or even how Iroha met him. In most timelines, it's possible Kyubey was chasing better leads, while that pebble somehow made Iroha a more immediate prospect; Ui and friends probably weren't on the radar for whatever reason, with Iroha's wish causing Kyubey to look into them.