^Just because Yukari claimed Reimu would have had to exterminate her if she became a youkai doesn't mean Reimu agrees or would actually do so. (Reimu herself never said anything). She also says Reimu's job is NOT to exterminate youkai but prevent them attacking humans and stop humans becoming youkai to maintain balance.
So imo she would do her best to stop a human becoming one, but if she failed to do so, what would be the point killing them? They'd just be a Youkai like all the rest she hangs out with. And given it happens very rarely- a lot less often than Youkai being born from other means, I can't see how 1 or 2 more in gensokyo would matter.
Another option for life extension would be through magic like patchy - or becoming a vampire? I admit none of them seem likely for her.
last edited at Aug 15, 2019 1:58PM