ANSWER:

One must not pray for the person who died as a non muslim as this is sinful and our Prophet salla Allahu alaihi wa sallam was ordered not to do it. 

Today an indian actress passed away.The whole facebook news feed is filled by rest in peace by our muslim sisters and brothers and the people argue when i shared that its not correct to ask for forgiveness as its stated in surah al taubah but then they quoted me a hadith that we should respect the person..ok even if we are respecting is saying rest in peace ok thoughshe died in state ofkufr?