I mean she has the lore where she was put in an orphanage and every time the orphanage tried to sell her Etwahl, it would always mysteriously show up on the doorstep again whether by being returned or just showing up out of the blue, then when Lestara Buvelle heard of the unique instrument she traveled from Demacia to Ionia to go and adopt Sona and left a generous donation for the instrument as well. (Sona was trained by Lestara btw) which arguably isn't alot compared to say
who literally has no lore now due to summoners not existing, their is literally no explanation for how he is on runeterra now since he was summoned originally by a summoner who committed some crime and fled to a different part of the institute of war, now his lore is you brought famine we are going to hang you up in your own field to die, cause why not??
Also for you daily bonus trivia tip Sona's adoptive mother Lestara is Directly responsible for Quinn's brother Caleb Dying when she and her family went upto the mountains of Uwendale to go hunting and encountered a Tuskvore ( picture a mammoth but much larger) and Caleb pushed Lestara out of the way and got gored himself, Quinn fell into a deep depression after that and a few months later went back to where it happened and found a wounded Azurite Eagle and they both got attacked by the same tuskvore but they managed to kill it when valor took out it's eyes letting Quinn shoot it with a large amount of bolts.