My (Removed) married a Hindu after lot of convincing her to recite kalma. Before nikaah, she did recite. But its been 3 years now she is not praying namaz. We tried to talk to her explain her things but she is not willing to listen. What should our behavior towards her?

If she admits that she is Muslim, then the marriage is valid, and you need just to advise her.
If she acts as Hindu, then the marriage is void, and he have to separate from her.