@Sansith,
I'm, an older woman in the US. I don't know where you live, in the US? in India? I don't know about your cultural mores re courting and marriage and the power of parents where you are. I don't know what your girl (girl? how old are you two?) is really feeling for her ex. People know love differently, and if she dearly loved him, that makes a difference in how soon she can really love another person. If she now loves you, that is, as I said, good.
What is the ex doing to interfere? If he is actually stalking her and she is in fear, then Tsar was likely serious, and a restraining order could be useful.
Other people will be along to read this and give opinions. A bit of added information from you could help.