I made that post half in jest before going to sleep, but to be serious -
Freezing or melting feats do not necessarily require AoE observation in the conventional sense (did it destroy a building, a city, or a mountain, etc) because it uses Specific Heat to crystalize humans or trees, rather than explosive force. For example, the D&D Red Dragon of VSBattles is given the 13 kiloton (Town level) treatment for his fire breath, even though his feat is only 18 meters long and 12 meters wide (about the size of a small building), and sustained over a length of time, because his energy to melt is still that level even with a very small AoE. It does not mean that Emilia's feat would have Mountain-level AoE or something, it would just indicate the feat's energy equivalent.
Likewise I only need to get the surface area to make the calculation, and make use of one of the similar methods already used for other freezing feats in VSBattles.
The surface area needed for this calc is that of the Elior Forest. Average tree population density for that surface area would be applied to freeze the given number of trees there. Or I can just make use of the volume of air and convert it to mass.
http://rezero.wikia.com/wiki/Kingdom_of_Lugnica
Elior Forest: A dense woodland forest currently owned by Roswaal where the Elves once lived. It was frozen over by Emilia in the past.
Or even just the population of the Elven village, if it's not the whole forest, and its distance from where Emilia fought Pandora, so that I can estimate the surface area of the village and the land between them.
In the ensuing battle her aunt is killed, Betelgeuse is driven mad and Emilia's powers goes out of control and freezes the entire elven haven.
About the instant thing - well I don't know, because unlike explosions that are instant and can be distinctly singular or multiple, almost none of the mid-high freezing feats have received the instant timeframe treatment (except for those that freeze a small number of people or something). For example, the Snow Queen's Island-level feat would take several hours to manifest and reach its maximum distance (at which point its energy was calced) in the actual movie, but it was still power-scaled to Elsa's AP.
https://www.youtube.com/watch?v=bE7R57nvNt8 (3:08)
So anyway, what method do you suggest then to quantify Emilia's feat? It isn't necessarily 'Mountain-level', I was just joking about that. But it still needs to be calced at some point by measuring the surface area of the place she has frozen.
(Actually, the feat is more impressive than purely real-life energy equivalents because the frozen state has persisted for more than a hundred years until Emilia awoken 6 years ago, meaning that the magic had been persistently counteracting the ambient heat loss for that time)
