If a person is not a carrier for a particular disease, the status of that persons’ spouse is irrelevant, so there is no need to inform her.
I’m not necessarily advocating for (or against) telling. I’m just curious as to the classification of such material as Loshon HaRa.
There are many things that one should not say, but not all of them are Lashon HaRa. Sometimes (as it might be in this case) it’s better to be quiet without it falling under the rubric of LhR.
The Wolf