The problem is related to the definition of "supernatural" as referring to ontologically basic mental things.
Not everyone who believes that a stone is healing power believes that they are ontologically basic.
A stone that does "healing" would be like having a type of acid that only dissolves shirts--it has no way to know whether something is helpful or harmful any more than the acid has a way to know that something is a shirt.
If you have an ill person telling them to get a good nights sleep, helps them heal in a fairly diverse set of circumstances. The advice isn't helpful in every case.
Frankly, any stone that was powerful enough to "heal" is something I wouldn't trust since pretty much any singificant "healing" effect could cause really bad harm under the wrong circumstances.
The question whether or not you trust the stone is irrelevant to the question of what's a useful way to check to CronoDAS girlfriend.
In practice she might tell you: "Duh, of course I check with a trustworthy spirit whether the stone is right for the particular occasion."
A quick googling for hematite suggests that it's supposed to grounding and balancing energy. Given that the girl is ungrounded to the extend that she sees spirits, from her perspective getting a stone to ground herself makes a lot of sense.
Not everyone who believes that a stone is healing power believes that they are ontologically basic.
But she is actually treating healing as an ontologically basic concept, even if she doesn't understand that she is doing so. That's enough.
She thinks it's possible for a stone to heal and do nothing else. It's not possible, unless the stone contains an intelligence that can determine whether a physical change made by the stone is "healing". It's every bit as absurd as having an acid that only dissolves shirts.
...In practice she might tell you:
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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