Hair Extensions.
Because if you see Divya in real life i.e. Antakshari, award shows etc. Her hair is a good few inches shorter. But in the serial its so long. (I'll try not to complain here). So they're most probably doing all this on purpose...showing an old fashioned Vidya for now who will change.
BUT I wonder how long after Saagar's recovery will she change her look. Hopefully not too long, I don't even mind if its gradual instead of showing it so obviously that she has gone to the parlour. 😆 A natural progression would be better.