Yes & No. I think Deepu is doing a really lousy job of explaining his relationships to Poonam, and by now, he should have explained to her all the interpersonal tensions b/w different family members, e.g. his dad vs his mom, his dadi vs his mom, Jyoti vs Sushma, their relationship w/ the Vashisths & so on.
Instead, he tells her nothing, w/ the result that Poonam is left asking such questions to Jyoti, and embarrassing everyone. Okay, why Jyoti left w/o telling is one thing, but Poonam's question - why is nobody in the loop about anything that goes on in this family - is a very good one. And when the family is struggling to make ends meet, it's not immoral of Poonam to question the sanity of Jyoti's not taking money from the Vashisths. Yeah, sure she can work 2 jobs and all that, but how is risking her own health and that of her baby good for Jyoti or her family?
And Sushma is largely @ fault for a lot of things. When Deepu threatened to slap her, it was after she had done what she could to upset Poonam, who, after being shocked @ this little known custom, went on to offer Sushma any other sari, but Sushma had to be insistant on that one. Yeah, Deepu could have disciplined Poonam for bad-mouthing Sushma on Holi, or calling Jyoti a step-sister, but aside from that, a lot of the provocations here have come from Sushma rather than Poonam.
And if he's being sissy, it's thanks to Jyoti trying to tell him how to be a hubby. First, he expresses his reluctance and unreadiness to marry, and so what does Jyoti do? She forces him to marry, and then starts giving him bhashans on how to manage it. Pity Deepu & Poonam.