I wouldn't get particularly excited about the individual involved - what matters that the cause of her death is either regime infighting, or some maskirovka aimed at providing an excuse for X or Y action, and securing wider public/elite support.
The target, either father, daughter, either or both, were in real terms nobodies: it's ether internal squabbling, or they were 'famous, but not important' goats tethered up for sacrifice.
And no, I don't believe the Estonians or Ukrainians would go to effort of sending a Kill team to Moscow, do all the surveillance on the targets, the safehouse, the counter-surveilance, the legends, and the political risks of detonating a car bomb in Moscow just to whack a nobody.
Putin? perhaps, Shogu, sure? But these guys are late night GBNews freaks. Worth a cheap letter bomb perhaps - if you can keep it clean and stay innocent - but not the price of a full on kill team in the heart of the enemy...