@MagicBananas probably because she had no one else, and she probably remembered that the mailman was going to be there.
And as to why did he not stop her idk i'm not the author
222 lip balms from what is visible on the shelves each one costing ¥104 so ¥23,088 for all that lip balm and there is probably a lot more that is not visible in the drawers and on other shelves. That's an expensive hobby but I approve.