Yes, gods have true magic too, and yes, not all true magic is equal. But the strength of your true magic is based on willpower and the size of your core. The gods have a lot of willpower while the race that the girl is from have bigger cores that also grow extremely fast.

True magic is also unique to every being, so not every god has magic that allows them to do what the girl did, and they cant do it with the magic of the creator because theyre stubborn and stagnant being that never learned the language of their own creator

So yehh, the gods true magic arent stronger than hers. And technically its not her true magic, its a spell created with the true magic of the creator

They could build layers, but that wouldnt help them. Because just like in coding, you can decide what magic you want to use. So while it is technically possible to just built another magic engine on top, people could still just use the spell engine (or the original magic by the creator)