Lapis is a very interesting character and I definitely can't blame her for still being somewhat hostile to the crystal gems as it was their was that caused her 6000 year imprisonment when they must have known the mirror was being powered by a gem (of course I can't blame them for not freeing her either as they wouldn't know it wasnt an enemy but if they had lapis may have helped them after what homeworld did to her). Meeting Steven is the only good thing to have happened to her in those many years so hes also the only one who could successfully try to get her to see any joy in life