I don't think there was any way to get Kavya out of the Mittal house, without hurting Aarush, logically.
Like Jahnvi said in the first week, Kavya is involved ipso facto because she married Kabir. And Kavya multiplied problems for herself by following Jahnvi everywhere, like after the commissioner's house. She literally walked into the trap, which Jahnvi hadn't even laid out for her (the locker)
Jahnvi never said she wouldn't harm Kavya. She only cared for the repercussions on Aarush.
Still Aarush was lucky, he got away after two months, he has his mother, his grandparents, who are nice to him. In future, Kabir might even bring them back.
Pooja had nothing, she lost her Dad and saw him being murdered, thats literally ten times worse than what Aarush had to see.
Pooja might have actually done Kavya and Aarush a favor, imagine growing up with a shitty grandpa like PK, who would keep insulting his mother, even without Jahnvi's acceptance. You think a man like PK would ever accept Kavya? And not taunt about Vyom? Well, whatever happens Kabir should keep them away from PK, even if PK comes back from the dead in future.
Sorry, I like Kavya individually as a character, but whenever she becomes the superhuman-bahu she gets annoying, and I can't help but think that Pooja is right to teach her a lesson. I mean, PK was cruel to Kavya too, why did she support him against Jahnvi? Mahaan ho toh ab bhugto, and because of her Aarush suffered too. He was collateral damage.
It was impossible to always protect Aarush from the consequences of taking revenge on Mittals. If Kavya and Aarush were with Mittals right now, they would be homeless too. Wouldn't that be a greater hardship for the child?
And the Mittals, senior Mittals, deserve to be homeless.
I feel bad for Dhruv, Kabir, Jai Sonali, but they are educated, they can get a job.