Out of jealousy... she is jealous of the fact and cannot stand anyone happy... there are people's like this not necessarily have to be ex gf... here they shown it but there are people like this... out of course when they do not get what they want then they chose two way...
one way- they helped to reach their goal ...
second way - they not let anybody be happy...
Dips is a case of second way... she is become so cunning inside that she cannot stand that a man to whom she left over like a jerk one day is now superstar with every possible money and he have a wife who rules it... when the man for whom he left RK is you know??? should I need to say... but you know what sometimes I feel Sikki don't deserve Dipali... if Dipali wants then she can better his life... but no she is just jealous... director just want to show this I guess.