Yeah, that’s pretty much the exact opposite of a plot twist.
Anyway, I know we’ve talked about some of this before, so I’ll keep it brief.
Distance from the shooter doesn’t matter much for the wound unless it’s at point blank range, or beyond the weapon’s effective range.
Treatment is always pretty simple, at least in concept. You take some silk and sew shut anything that looks like it might be leaking. Of course, finding everything that’s leaking can be an issue, particularly when there’s blood everywhere, and you’re having to tear open tissue to find the tissue that was already torn apart.
Off hand, I can’t remember if lower left is a kidney or the liver and a kidney, either way, this is a wound that will kill your character if left untreated. There’s also the possibility that the bullet would perforate the intestines, at which point she better hope her surgeon finds it, or she will die from it. (Also, remember, A&P is not a part of my field, so I could be hilariously wrong here.)
Depending on where the bullet embeds this could be irrelevant or a death sentence. If he gets shot in the gut as well, I’d say that’s unlikely, but bullets don’t really seem to enjoy obeying physics when they think it’s not looking. Again, getting shot in the torso, pretty much anywhere, is not something your character will walk away from. And there are quite a few organs that will flat out kill you if you damage them with a bullet. Also, the bullet does need to come out. Unless it’s managed to find a home somewhere that can’t be removed, which is somewhat unlikely with a gut shot.
The part I know we talked about before is infection. Bullets are effectively sterilized by the firearm. So, blood loss is a risk, but infection from the bullet isn’t. But, if we’re talking 1860s, there’s no disinfectants. Alchohol’s primary use in surgery was as an anesthetic, not an antiseptic. The surgeons weren’t using dirty tools, but the practice of sterilizing equipment just didn’t exist, and there wasn’t a clear understanding of how to treat or prevent bacterial infections. Short version is, unless your characters are extremely lucky, they’ll probably die.
Also, I don’t know if you know this, but mid-nineteenth century Russia was, let’s call it, “very energenic,” politically and socially. The country was going through massive changes in an attempt to modernize and shake off the perception of being the backwoods of Europe.
Russia was still in the process of abolishing serfdom, this started in the mid-eighteenth century, and ended in 1868.
There were efforts to transition to more democratic monarchy, with the creation of local governing Dumas. The national Duma wasn’t founded until the 1880s (if I’m remembering correctly.) Internally there was a lot of friction between traditional cultural identity and imported ideology from Western Europe.
I want to say there was tension between the protestant denominations and the Eastern Orthodox Church, but I can’t remember the details, so that might have been minor or a non-issue.
If you want a better look at all of this, Fathers and Sons by Turgenev is a good jumping off point for the cultural tensions. Also, although his work tends to be dense as spent bricks, almost anything from Dostoyevsky will be helpful, though (and you may hate me for this) Crime and Punishment is probably the place to start for the timeframe you’re talking about. The Brothers Karamazov might be useful as well. Just remember, both authors had their own agendas.