Kumud, due to fate or by her decision entered into this marraige, and is now trying to make it work. She wants to try all the ways to make it work before deciding to come out of it. Some people have higher threshold for pain than others, everybody has a diferent breaking point. She will try until her "Himmat" breaks. Even though Pramad is bad, rest of her in-laws love her. So she wants to reform Pramad for her own good and also for the family.
Once Pramad turns good will she be able to accept him as her husband in all the ways is to be answered (please Pramad continue to be EVIL). She has a soft corner for Saras and loves him(platonically of course) as a friend and confidant but not as a lover.
It's not her ego or pride which is stopping her from going back to Saras, while she is still married to Pramad she wouldn't even look at Saras in that sense.
She doesn't have to bear any abuse from Pramad, being a strong character she is still standing up. If she was "Abala Nari" she would bear all the atrocities and resign to her fate, but she is fighting to reform him and there is strength and resolve in her silence too.
Where is the story if kumud comes out of the marriage as soon as she knew the truth from Saras for breaking up the marriage. Since this is the story about their journey as SoulMates and how their love finally found it's happy ending we should be patient and let their characters evolve. (It pains me a lot seeing Kumud in tears all the time, in real life who can bear so much pain)
Eloping with an ex-lover(no matter how much ever mahaan he is) doesn't make an ideal character.
Hopefully CV's will keep the final ending in mind(SAMUD forever...) while introduing their twists...