You know what is pathetic about this situation is that it has nothing to do with the characters, it has more to do with ekta kapoor and her writers, they wanted to create drama and found the most ridiculous, unbelievable and laughable way to get it done.
Just think about it, this is purvi we are talking about. What do we know of her, do you really think she believed arjun cheated on her. It is too beneath her to have such jealous feelings especially of her sister who she initially sacrificed so much for and loves dearly.
Ovi did what was best and there is lots of difference between what she did and what purvi did regarding the baby matter. Infact I would even take it one step further and say Purvi's lie was self serving, idiot, and destructive.
What a shame purvi turned out to be a mother of fools in all this, ekta made her one and no one will forgieve her. Everything could have been justified, what archana did all those years ago regarding Soham her heart was in the right place, even purvi giving up arjun was for a good reason even if it was foolish, ovi forcibly wanting to marry arjun she is not evil so it is ok, but not this because it is plain cruel. If purvi has been cruel to Arjun how can it be pavitra rishta. Even at the lowest point of archana and manav relationship I never thought they were cruel to each other, even when manav left her I thought it was justified because their son died because of her stupididty and marriages can end over this it is very realistic.
To summarize Arvi should not get back together. Purvi's real punishment is when she finds out the real truth and wants to get back with Arjun, he tell her to get lost.