Although Tulsi committed this act, I don't really think she should be blamed for this.
Tulsi carried out this mercy-killing act at a time and a condition when she was emotionally wearied out by Savita's constant persistence to die. Savita kept pressing that she can no longer bear the pain and she convinced Tulsi that nobody will blame her. She even led Tulsi's hand to the LSS's switch.
I don't think when Tulsi came to meet Savita that day, she knew that she would end up doing this. She actually came there to encourage Savita to live. However, stubborn Savita emotionally blackmailed Tulsi in doing the act. Tulsi didn't even have time to think about what she was doing. She was not even in the right state of mind. No wonder she didn't call anybody before doing this. She just kept following Savita's commands, be it turning the switch off or grab a tulsi leaf.
But, Tulsi DID realize that she didn't even inform anybody (if you watched the episode closely). But, it was too late then, she had already let Savita go.
If you put yourself in Tulsi's position at the time and place of the incident, you will understand that it's easy to say that she should've done this or done that, but it's not as easy as it might seem like.
Many times in life, we do things, or say things, without conscious thinking, in a very emotional state of mind. We would never make any mistakes ever if we performed each activity with conscious reasoning.
So sukhi, how about at least a little sympathy for our Tulsi?