[spica308]

I shared her earlier words about Mithra, she will stand by it, she has always stood by her word.If she decides she is doing harm to Mithra and she believes Mithra loves Tharun wholeheartedly she will sacrifice Tharun again...that's her

Tharun wouldn't have choice if Nikita decides that, he was able to get her all this time because she was the one who decided to stick to her commitment not because Tharun was controlling her like you mentioned. You keep saying she lacks maturity but I do not think she is immature, she just sticks to her choices...She chose Jay, she stick to him for a while until he encouraged her to flirt with Tharun, that day if Jay fought with Tharun and stopped him from flirting his wife, we wouldn't have seen this day....

 Now Tharun did not fight for her with his ex, it is clear that Mithra already fought with his parents, made them agree for marriage...so she is deeply in love as well. 

~ RCF

Maturity leads you to make correct choices. I thinks she has made impulsive choices -- not necessarily correct.
No point arguing more, end of the day it is a sex story.