Except the game doesn't use it as a euphamism at all. If she wasn't literally selling flowers then they would be.
Lol, so you actually don't get it
Ok lets make this very simple just because something can be used as a euphemism doesn't make every use of that phrase a euphemism especially when it's literally someones fucking literal job title.
OK let's make this very simple: When it comes to any art form, truth lies in the eye of the beholder. If I think a painting looks like a duck, and I have a reasonable explanation for why it's so, the interpretation that it looks like a duck is valid. Others might think the same painting looks like something else. That can also be valid. There is no absolute truth, and (I know this is a controversial thing to say in a place like this) the painter/author doesn't really have a say. The painter might have intended the painting to look like one thing, but that doesn't in any way invalidate another interpretation. In the case of FF VII, the context is that there's a girl living in the slums, and she's known for selling flowers. In Japan, selling flowers is a euphemism for selling sex. Is it thus a reasonable interpretation that she is, indeed, a prostitute, but the narrator chooses to use a euphemism rather than spell it out? Actually, yes. It makes sense. This is a story where the player is told a number of things that turn out not to be true, so we learn that the point of view isn't reliable. Additionally, the narrative is from Cloud's point of view, and we know he likes Aerith so it makes sense for him to use a nice euphemism. Like mentioned before, it also fits with her demeanor surrounding the whole Honey Bee Inn incident.
But remember, this is one interpretation. There is no absolute truth when it comes to consuming fiction. I'm just saying that it fits. And the fact that she "literally sells flowers" in the game isn't in any way an argument against it, since that's part of the fucking euphemism, lol.
There is an absolute truth regarding Aerith, and that is that she literally sold flowers and wasn't a prostitute. ---