Reimu did go all Nanoha on Iku, but it's entirely possible she learned her lesson about jumping to conclusions from that incident. Either way, she is a worry in so far as being a youkai around angry Reimu is always a worry, but we've been helpful and, more importantly, not obnoxious or obviously responsible, so I think that will stay her hand.
For the record, I think Ran glancing at Keine is a reference to the resolution to OkQ, because Yukari has since learned what the shit went down so it's entirely possible Ran knows as well. This is far more speculation than any other reference I've made to past quests, though, and I would not bank on it. It's entirely possible Keine's shenanigans are just inherently "not normal magic". Given what she can do, it wouldn't surprise me.
Also, for as much as this shouldn't be a worry because I expect to be home from work before Purvis gets back, there is one small bit of flavor fun I want to have before we leave Reimu. The Koishi question obviously needs answering first, though.