I personally really like her with Onir. He is a really sweet guy and she seems really happy with him. Plus, for me I feel that If she is with Onir she doesn't have to deal with half of the things she would have to if she were to go back to Arjun.
Arjun is married and is about to have a kid with Ovi, and I know many people say maybe the kid is not his, but till that is proven, I am going to assume that the kid is his and he really should have left her before she had the pregnancy go so far. I know that many people divorce after having kids but the sole reason why Ovi decided she was going to give birth to this kid is Arjun and he should take responsibility of it and stay with her.
The reason why Ovi and Arjun's marriage is not a happy one is because Arjun is always thinking about Purvi. If he were to move on, which I think he will now because he now knows that Purvi is married and has moved on and there is no way he can go back to her again. They both have separate lives that can not cross roads again.
The biggest reason I love Onir and Purvi together is because they look so cute and happy together. They just seem like the perfect couple even if there are some things that are hidden I feel like they will be able to work through all of that and move above that. They are adorable together and hopefully they stay together.
Riya