She can do it now since she is with child and Kunal by no means can deny it. Mauli can still go ahead with divorce citing the reason of adultery which is still a civil offence under IPC and Hindu Marriage Act and can guarantee immediate divorce to the betrayed spouse.
So, Mauli ask for alimony and if Kunal has a change of mind even then stick to divorce and if he doesn't budge then threaten him with adultery clause in the divorce case.
I know case has been fied and new clause can't be added now. But makers have already played with a lot of facts, so playing with this one more fact won't be a big deal. My mind would get sadistic relief in watching Kunal being screwed by every possible way. Letting him go easily is too little of punishment.
But Mauli is Mauli and she wouldn't do anything like that and That's why there are times when I hate myself for loving her so much, especially when she goes sensible all the times.
One has to become shameless to show shameless Kunal a piece of mind. Since Kunal behaves no less than the entitled brat, Mauli can try that too sometimes and I would take that like a pinch of salt.