Mj was trapping maya in his fake love is a sin as he is very much aware of the fact that what he is doing with manvi and manvi is actually at fault for falling in love with but rest of the family and aamir has there own role in destruction of manvi in earlier fb during mask party it was clearly shown that everyone except rishi and rudra welcomed her very lovingly infact manvi tied rakhi on aamir's hand he is a brother figure for manvi.
As for rishi's murder it is not the part of maya's intial plan but when rishi joins ruan company rishi becomes a threat and maya decided to kill him . In same way she decided to kill rudra after mayra death enraged her revenge but rudra's love for her save rudra's life and maya married to rudra due to love for him but at the same time she is decided to take revenge on Mj and all the culprits but spare the innocent ones like ananya.