It's just a part of her character that doesn't define her completely.
Why does she need to have a justification for being lesbian?
If she had the love story that some people are asking for instead of her actual lore, they would then claim that it is forced and it doesn't belong into the game even harder.
Apparently, it's never a good time to introduce a LGBT character because it's always due to a political agenda.
If there is something that I like about League, it is its variety of champions from A to Z.
Some of them may have similarities but they all feel unique, and there is no problem if you identify with a champion and you enjoy playing him, it's a game, play whatever you like.
Not every champion has to be the edgy guy with a dark past, diversity is the key to keep the game fresh.
Thanks for reading, I don't usually come to the boards but I wanted to share my opinion about this topic.