Similar: Sismance, multiple mains, FLs were friends in school; FLs band together to uncover truth and deal justice; interesting FLs, independent FLs. FL-centric plot.

Differences: PS I Hate You is based off a suicide and has a hefty dose of romance + relationships + desire, webs of lies, buried secrets, and more...dark. It touches on drugs, sex, violence, hate, envy. Bridges are burned.

Danger of Her focuses on friendship and work instead of relationships. It touches on sexual abuse and abuse but no drugs or violence, minimal envy and hate (not to the degree of PSIHY). About building bridges, not burning them.