I gotta say, I am annoyed by this turn of events
This wasn't hinted at until now and feels like a complete asspull, there was never a sense of sadness about her lack of a future mentioned by anyone at all. It's an explanation why she's cheerful and that doesn't need to be explained; and it makes the relationship in this idiotic rather than moving. If it's been hinted that she didn't think she had a future before this, it's possible I missed it, and if it was hinted that the dude killed himself before this, I missed it as well. But from my standpoint it's outta nowhere and an annoying revelation about how these two kids ended up dying in a field.