The meme of Memeira is more nuanced than one may think at a first glance, it goes beyond the joke about balls, stealing the joke much like how she wanted to steal the Hakurei orbs(balls), and thus ironically becoming a meme herself by doing what she was supposed to do within the game.
Meira is an unexpected character that appears unannounced and is supposedly not affiliated with our current antagonists, she butts into Reimu's path, practically forcing her way in on dragging Reimu into a danmaku battle, not only that but she introduces her balls for bullets into the game, praying for as it bounces around the screen.
However, with in mind on how she's showing up out of nowhere(Meira out of nowhere) within our hero Reimu's path is also why she's in the hearts of so many /v/hoes on the first place, as it's in part of her very soul to behave like such.
Not just that but her legacy never dies, in future games she appears once more, and another within a manga. It's her but not really, the appearance is very similar but is completely different in terms of personality, only highlighted by deeper references when it comes to religious figurative applications in japanese mythology and lore.
But there's also other applications outside of it when it comes down to her design which was practically double stolen from another game and an ancient manga which ZUN liked and decided to hijack on having within his game, the first of many and the true soul of Touhou on what turned ZUN into what he is today with his doujin spirit, borrowing ideas from other creators to make it as his own.
Meira, much like her much rich purple hair is tasted like fine wine, it takes some acquired taste to get used to but by then, you'll learn how vintage it was on the first place because by then, you'll realize how important she was not just in term of lore but also on carving a path forward for our beloved ZUN.