Her smell ability isn’t a “skill”, it’s more of a quirk. I don’t expect it to be a tide-turner ability in combat, maybe as a scout-ish ability. But like in many other stories, quirks like these add to the character’s uniqueness, and that’s probably it. Not because she is S-rank nor because she is strong; but just because she has that special quirk.
She did mentioned a lot how he was “the first to smell nice”. So this does not exclude any hunters, even high-ranked ones. I am very sure this is because MC is not gaining levels naturally like other hunters who have to shed blood and have killing intent. It is also similar to the Elf leader who said he can’t detect his killing intent as well.
For now, not very big deal. But I am expecting this will ties greatly with the origin of the “game system” and MC’s unnatural progress.