Is it just me or is anyone else wishing there wasn't a magic cure for her? The goal of having to cure your real-world disability before you can be any use is never a good lesson and I think having a wheelchair-bound lancer would be much more orginal and just plain awesome.
There isn't a magic cure for her.
She's not disabled in the general way, her body is just extremely weak probably through genetics. What he's having her do is strengthen her body in a way that normal medicine can't do for her. By absorbing those crystals she's getting her weak muscles up to a normal person's level which to a normal person would make them pretty damn strong. Same way Karen's friends are using them to become smarter.
Yes, it's a way not available to the average person, but they have to work hard and risk their wellbeing to do it. The only "magic" is that she has a cheat character right there with her giving her high level gear and making the risk less than 1%.
As for a wheelchair-bound lancer, meh not as original as you think. And I personally find a wheelchair filled with ranged weaponry far more effective and awesome and though that too isn't at all original.
While lances were a great hit in medieval warfare, they were still one-hot-wonders. Even if it didn’t shatter after initial hit, it was absolute nightmare for a following melee. Hence they became associate only with jousting.
Better weapon would be either curved sword (like scimitar) or good ol’ mace to break some bones. But even better yet is ranged weapons like bows and firearms. I can imagine that two-handed bows are out of question with manual controls of the wheelchair, but for sure there should be a rudimentary firearms that work on monsters, right?
Maybe later but currently she doesn't have the physical strength for melee unlike Karen. Curved swords and mace are rather lacking in reach power seeing as how it needs to be strapped to the wheelchair for usage. A mounted firearm should have been what he gave her as a bow or crossbow still wouldn't be ideal with her weaken body.