The article you have provided is a Reddit article, which is a website known for not having reliable information. The article only shows a screenshot of the title, without any information backing it up. When looking up the title, the original article was not one of the first to pop up but I did manage to find it. (
https://www.storypick.com/2nd-wife-kills-3rd-wife-with-1st-wifes-kids/) The article was more about the backstory of the marriages rather than the actual murder. There is also a lot of gifs in the article which isn't very informational. It almost makes it seem unserious and that's not professional when talking about a murder. I searched another article about it and a lot of it was filled with speculation of what actually happened. (
https://www.onmanorama.com/news/india/2019/03/08/mumbai-murder-second-wife-kill-third-wife-step-daughters.html) In the article, it claims there could be two possibilities of how she was murdered, but they are both presented as theories rather than being leads backed up with evidence. So no, I don't think this story is entirely true. There may be some truth behind it, but the articles don't make that clear.