^ Jenny, different versions of the Master(s)
Jenny had still recently been created. The new show has suggested a certain lingering regeneration energy that heals you without transformation early on in the process. If Clara starts shooting electricity from her fingertips, the Master argument will have more merit.
Assuming she's a Time Lord regenerating would mean that we witnessed her final death, because you aren't regenerating from being turned into a Dalek. I doubt they'll do that twice. The whole arc would directly parallel River.