It's quite obvious that she trained, if she didn't she would have been complete fodder during the Aldoron Arc, which she clearly wasn't.Demon gates can solo. BSS Mira (while being controlled)>Skullion (who is stronger then everyone here except for DF Nebal) and base seilah have proven to be above BSS mira and in etherious she one shot satan soul sitri. sitri>>>halphas>>>>>BSS. Torafuza and tempesta also have scaling to be above BSS mira and on the same level as Satan soul sitri if not above (Due to scaling to laxus and seilah) and no mira did not get stronger since she did not even train so what makes u think that torafuza,tempesta,seilah,kyoka and silver can't solo on their on?
So, since Juliet and Heine were pretty much no/low-diffing BSS Mira that means Juliet & Heine>>>Dragon Eaters by your logic? It is absolutely ludicrous that everyone but Mira improved.
Do you have any proof that Mira did not get stronger?