The decklist is definitely a cool one I might consider improving upon with Gardevoir GX coming out soon-ish! Some things that I might note about the deck, if I may:
The reason it doesn't seem as competitive, as
@CrownAxe has noted, is that it isn't as strong as Volcanion, and this is for a few reasons:
-Volcanion doesn't play evolutions, except for the odd Starmie and Octillery
-Volcanion has very quick energy ramp with Max Elixir, although M Gardevoir can match with Mega Turbo
but the primary reason:
-Volcanic Heat with Steam-up hits larger numbers quicker than Xerneas Break or M Gardevoir-Ex, as
*2 Volcanic heats knocks out Exs and Basic GXs in one hit (190 damamge), which can be achieved in one turn
*This takes 10 energy for Xerneas Break and 7 Energy for M Gardevoir-Ex , which takes at least 1 turn for evolution and 1 Geomancy to get the necessary energy
Now, this is still fine especially how much slower this format has gotten, and the difference between a 1 turn and 2 turn setup is pretty inconsequential, especially since Garbodor's Trashalanche is there to punish decks that are waaay too quick, as items are the primary tool for fast setups (aside from Shaymins and Tapu Leles). If your slower setup, though, still uses a handful of item cards (to allow Garbodor to knock out your attackers, 7 items and Choice band for Gardevoir-Ex, 9 items and choice band for M Gardevoir-Ex) to setup, this is where Volcanion will simply perform better, especially when it has item-less setup tools like Brooklet Hill and Starmie.
It might be fun to try this deck as Gardevoir-GX and M Gardevoir-Ex, although now that I think about it, that deck seems too clunky as it would run too many evolution lines.
Definitely looks like a fun and pretty consistent list, though! Congrats to your daughter being able to pilot the list so well! Honestly, being able to play a deck well is sometimes better than running a meta list.
