I disagree.
Firstly, the advantage isn't as significant as it seems...
Secondly, nothing is said about the stats and level of the heroes; it would be good to take a look at the save file.
And finally, the most important thing: it's Nela, after all :)

I calculated it based on the numbers - the total HP of Enika's troops is 8300, and Nik312's is 4300. That is, in terms of raw power, the advantage is twice as large. Therefore, to negate the advantage in troops, Nela needs to attack with lightning for 7-8 rounds.
At the same time, she needs to eliminate the archers so that they are not decimated in the first two rounds of the battle with angels and pegasi. And don't forget that battles involve 2 adjacent stacks.
The only thing that can save Nela is having a direct bow and a vulnerability orb (to slow down and apply lightning to the dragons); in other scenarios, the battles on the flanks will simply overwhelm 8/10 of the opponent's troops. And it might also help if Kir visited a tomb and the troops are demoralized with each turn.
Even though I'm a newbie, I wouldn't lose to even a super-experienced hero in this situation.
Of course, all these statements are based on the assumption that the stats are approximately equal.