Whether or not it can be deemed realistic or not, you can’t exactly apply those standards to a game where one choice is final, as in real life you could potentially explain yourself and try to make amends. I figured if someone did die, then she would hate me since I promised nobody died and then they did. I didn’t know the circumstances I was entering into, so to just assume that I had all the answers, that’s just dumb. As for apologizing, that’s another option I wasn’t aware whether or not it might be available or not. If I did promise, then I would enter into an agreement to actively follow a path that A) may not be available and B) might jeopardize/nullify my own goal.
That kind of selfish stuff ought to go both ways then, and she should have done anything for me, that she ought to have had my back when it really mattered to me. The reality is there’s always going to be a taker and a giver in any relationship, the scales may tip sometimes but the roles tend to remain mostly the same, so if she was as selfish as you seem to think, good riddens in that case. We’re talking about the realization of my imaginary life goal here, that’s like standing in the way of someone’s dreams, all over some faceless rando’s that might at best get a paragraph describing their faceless deaths. Or the life of the baddies whom nobody in their right mind ought to care about either. I don’t even remember her being described as some spineless hippie as I certainly wouldn’t have picked her as my RO if so. But then again my choices as far as I remember were; girl-next-door/childhood friend, spoiled rich bitch and smoking criminal so eh.
In any case I didn’t tell her her wishes were incompatible with mine (or rather didn’t intend to), if deaths could be avoided then great and that’s what ended up happening, but I didn’t know that option was on the table until after it happened. When I picked that option, I saw it more as; I’ll do my best. Rather than; nope gonna go on a killing spree. So again, a matter of interpretation. There wasn’t really any way I could guarantee for certain that nobody died even if that had been my goal, and lying about it was to me; the jerkass choice. Because hey, you’re lying about your true intentions to your SO, that sounds like a scumbag move to me at least. I’d rather try to be a good person than having others just thinking I’m a good person.
You can justify it any way you want, but the fact of the matter is; it was just one stupid choice between happy best ending and screwed over at the last second and that ain’t okay in my book. It was basically the equivalent of a light switch for our relationship, on or off, only worded differently. Look at any rom com, the bump-in-the-road/complication doesn’t show up at the end, because if it did then, whoops a misunderstanding ruined our relationship, the end. Now granted that just might happen in real life, but there’s a reason fiction is called fiction (no mention of GoT).
My point being; make the choices clear, if there’s any ways to misunderstand the wording on a choice, then right at the end is where it would be the most important to consider and try to fix that as you don’t want your readers to feel cheated when they’re that close to the end. Instead of yes or no, how bout a maybe or a I’ll do my best. Sometimes you might not even need to write a new branch as it’s effectively the same as another choice, only worded differently.