You should not abandon hope for her. Continue to encourage her, while not being forceful or pushy. Pray where she sees you and perhaps she will feel remorse that she is not praying.
A scholar in Najaf told me about being persistent, "I remember there was one of the youth who followed my father in taqlid and at some point he became a communist and left Islam. My father would pass by this youths shop on his way to salat everyday. My father would always say salam to the youth, but the young man would ignore him and never reply. My father kept saying salam to him everyday for one year then the youth finally replied to his salam and ended up repenting and coming back to Islam."