The problem is that both their lores are extremely outdated and the worst part is that Leona is actually stuck more in the past, since she doesn't react in any way to what Diana has done. We've got no idea where she was, what she was doing, or why Diana didn't run to Leona with it if they were so close, etc.
For all we know, we've got no idea how Leona reacted to Diana killing the elders or what Leona's own view of the Solari is for that matter. Only Diana's lore mentions the Elders as the baddies.
This is honestly my headcanon in short: In my opinion the killing of the Elders was a wake-up call for Leona to open her eyes to how they treated her and the rest. I think she'd remember more of her Rakkor origin and mainly stuck to her own beliefs, not someone else's indoctrination. That'd probably cause a lot of struggles between her and the rest of the Solari. I think she'd seek reconciliation, but that doesn't mean she wouldn't want Diana to face the consequences of her actions.
All in all in my view, yes, Leona is the defender of the Solari but definitely not someone who'd impose her beliefs onto someone and would be heavily against it if the Solari were doing that. That being said she values live and will protect those who can't protect themselves, but at the same time has no qualms about killing people in defence or other warriors if she were to go into war.
So if they turned her into some stupid crusader then I'm gonna flip the table. Also if they remove her Rakkor origin then I'm gonna die on the inside.
TL;DR: I'm not happy with the sound of where Rito's taking Targon's story, but we're yet to see just how bad it turns out.
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