According to a source on the sets, the production house makes sure that there is a bank of episodes, thus not affecting the show.
And when things get too difficult, whether it is a shortage in the bank, or a re-shoot, a dummy Tulsi is called in.
The source adds, "Even if the dummy thing does not work out, we use our last option - shooting with Gautami instead, and she is kind enough to accommodate." Otherwise the dummy is trained well, and her shots are clubbed with closes of the real Tulsi.
There is always a way out in the television industry.