By definition mercy killing is assisting someone in committing suicied - euthanasia - giving someone pills, or gas, or helping them take the final dose.
Pulling the plug is NOT mercy killing, that is simply saying that you don't believe in keeping someone alive with machines, and that either they live on their own, or they pass - ending the suffering, but not killing them.
There is a BIG difference and I think Ekta has shown a clear lack of understanding by calling this Mercy Killing. And if she isn't the one using this term and it's something someone else has termed, then we need to take a look at our understanding of English! Because this was not a mercy killing.