When you tell a person something is assur, rather referring them to a Rav, you’re issuing a psak.
While I haven’t changed my opinion that her statement was too big of a reach, I think you are overgeneralizing.
As an example, if someone asked you if you were allowed to open a light on Shabbos, and you said no, would that be a psak? No, because it’s a well known, accepted halachah. Someone may have studied a particular inyan well enough to answer a question definitively, even without being a “posek” per se.
Again, I don’t feel that this applies here. Saying something negative is by by default assur. In some cases, it may indeed be “toeles” to vent, but there aren’t enough details available here in the CR to make that determination.
Had a general statement been made that on occasion there may be a heter based on emotional needs making the saying of L”H toeles, I think there are people who may be well enough versed in hilchos lashon hora to say that, even without being a posek.