I think it makes sense when you put this on it's head. For the past 10 years Meeta has been Ashok's wife in reality while Babita is the one with the title. Meeta gave up her family, her self-respect, for her love of Ashok. She has been swallowing her bitterness regarding Babita for 10 years before the fear of losing Ashok made her desperate enough to follow him.
Meeta lives for love. She wears her heart on her sleeve. She's emotionally open and hurt and desperately needs a family, but unlike Babita, doesn't have the patience to build one. She also puts Ashok over and above everyone else while Babita doesn't.
As for Babita...I think as the story progresses we will see (along with Babita herself because I don't think even she's aware of this) that what she and Ashok had was never love (or even real). Successfull loving marriages take time together, effort, and hard work (even in a love marriage but this is especially true in an arranged marriage).