Vaccines aren't technically required for a k-1, however they are for AOS. And yes, they can just get them once in the US, but they'll pay for them here too. Not only that, but they'll pay for a civil surgeon to do an I-693 and perhaps another medical exam because it can be difficult to find a civil surgeon that will only sign off on the vaccinations. If a K-1 entrant has a completed DS-3025 from their visa medical, then they don't need an I-693 when filing for AOS as long as they file within a year of their K-1 medical.
OP> I suggest you have her get the vaccinations there before her medical, and take the records to have the panel physician mark them off on her DS-3025. AOS is easier with a DS-3025 that's marked complete. There's a pinned topic in the AOS forum with more info on this.