"Then she poses as a model."
Translation:Elle pose ensuite comme modèle.
That can't be the problem with using un because that is exactly what she is doing. She is posing like a model. Duo routinely uses like and as to be interchangeable words with very similar meaning. While that is not exactly true in English, it is very common to treat them as such. Both like and as draw a comparison. As means identical to, like means similar to. But Duo doesn't acknowledge that difference in their lessons. I'm sure that they aren't doing so here either.
The English Duo example is poses as a model but they reject comme un modèle. I would like to know what the issue is for future reference.
I am guessing it is because it is like a job, where in French they don't put the 'un' for jobs right? E.g. je suis docteur, il est ingénieur, if it was 'she poses as a teacher' i think it would be 'elle pose comme enseignent'? I'm not sure, but that's what I'm taking from this.
I'm surprised no one has yet noted the fact that "to pose as" something means to fraudulently impersonate.
Yes, models "pose" for the camera. But if this sentence is supposed to mean that "she" poses as if she were a model, you'd have to say that, or possibly, "she poses like a model".
If it's supposed to mean that she is in fact a model and is posing as part of her work, you'd have to make that clear. Perhaps, "As a model, she poses (as part of her job)"
I have no idea if the French sentence encompasses either or both of these meanings. I hope one of our Francophone colleagues will enlighten us.