Depends on how important she's going to be to the story going forward.
If she's mostly going to be relegated to a side love interest with her own storyline but which isn't crucial to the overall plot, it wouldn't be that difficult to allow her to die. It would mean people who fail to save her would miss out on any future scenes with her in them (and thus potentially risk getting a new update that is mostly content they can't see), but that's on them.
I could easily see a dev handling that particular juggling act if they wanted to. Whereas it would be much harder to do something similar with Marianne or Jessica/Rachel, because those seem key to the core story going forward. Or to put it another way, they're part of the MC's story, whereas Lisa is mainly just part of Lisa's story.
If anything, it almost makes more sense for her to die if you don't save her. Because otherwise you have to justify a relationship with her without having the huge moment of catharsis and revelation, which doesn't really work without a lot of fudging. It's much easier to just have a gateway moment, and from then on it's just a case of whether or not the MC is actively in her storyline or not.