Just like in the movie. Tom is indeed delusional, Summer is just cynical in her communications. They are both using shit software. Tom is putting all his fate on a single private company in pursuit of a misguided ideal and ignoring the red flags through rose tinted glasses. Summer doesn’t want to commit at all because she knows there’s much more complex factors at play than privacy alone but hasn’t yet found someone who makes her feel safe and secure the way she wants, so she settles temporarily for what feels fun in the moment.