>>281397634It's pretty directly stated that lain caused her to kill herself so she could be apart of the wired directly. She did this because she was lonely and didn't realize the pain she was causing. The girl told her at the end, "there's nothing easy about dying"
Lain felt immense guilt over it, like she felt over her other actions like spying on arisu. Everything she does in the show is because she's trying to understand people, not because she's malicious or violent, incase you're thinking that I think lain is a bad guy or something. I don't. Lain both is misunderstood and misunderstands others and the world around her. Her choice to separate and isolate herself at the end is done out of love for others because she still, at that point, doesn't know how to interact without hurting them