He married her after she became Muslim but she does not pray
Question

                I am a rational Muslim. I told a Christian girl that I would never be able to marry her because of the difference of religion between us. She agreed to enter Islam and I married her believing that she was a Muslim. We have now been married for three years, but it seems that she does not want to pray despite all my efforts. I bought her some Islamic books on this matter. During Ramadan, she started to fast with difficulty but she is not praying up till now. What should I do (if she carries on as she is)? I have started to feel tired of reminding her to pray.
Praise be to Allah.
      In this case you have to leave her, because in this 
      situation she has entered Islam and then left it, and this is regarded as 
      kufr, rejecting the sound religion and apostasy from Islam. If she insists 
      on refusing to pray and fast and do everything that is required of the 
      Muslim, and she has not given up haraam things, then we think that you 
      should leave her. Whoever fears Allah, He will grant him a way out. Allah 
      says (interpretation of the meaning): “But if they separate (by divorce), Allaah will provide abundance for everyone of them from His Bounty” [al-Nisa’ 4:130].