Were they new (sprout icon)? That might explain the issue. They definitely should have been using Vitra/Cure II by that point, but if they're new and just made it to Haukke Manor, it wouldn't surprise me if they're still figuring things out. A gentle reminder for them to use Vitra instead would have been the best option in that case.
That being said, if they weren't, then they're either leveling their first healer (in which case I might give a little leeway for this sort of thing) or incompetent. I've definitely had runs with healers still spamming Cure in HW-era dungeons, which is even more frustrating.