I do like the idea that it's the shide (streamers) that make the purification wand that's passed over the generations. Imagine one of the previous mikos having a purification arquebus.
So this is a detail in Double Dealing Character. Before the fight in Stage 5, Seija actually asks Marisa and Sakuya to join the revolution. However, she doesn't ask Reimu.
And it is also a partial reference to Seija's fortune slip. There is a fortune for "Tools" – Tools will never betray you. And thus to Seija, Reimu as Yukari's tool will never betray her.
Though personally, I like to see Yukari as at best only an ally. The Hakurei is not subservient to the Yakumo in Gensōkyō's political spectrum. Reimu nominally serves the Hakurei God-Emperor, so... she really is a tool 🤔
