That's not a very good example. Such a gift likely brought up memories of the past when she was ostracized and bullied for her preferences. So perhaps you should further examine something before trying to bring up that the author had "no idea what they mean." The word is well known and I'm sure The Observer knew exactly what direction he wanted it to go in, rather than it being some sort of mistake like you are implying.
I took that into consideration with that and other examples, it's still the wrong usage and I say that as someone who writes and edits semi-professionally. It's definitely a mistake based on the surrounding prose to that particular line and typical language usage of the word melancholy. If she were to grow melancholic (correct usage in that particular instance if they absolutely had to use melancholy) it would be momentary due to the mood. Due to the usage of increasingly in the sentence and from the surrounding text having her grow increasingly pensive or reflective makes far more contextual sense. And there's other examples littered throughout their writing of the same kind of contextual usage mistakes.
Hence I picked that specific example as the two sentence halves don't fit each other and clash. As without having to post too much of the scene for people to see as a potential spoiler it works as a good showcase. It throws the pacing of their writing off when honestly simpler writing would be more fitting and carry more weight to it.
For example, perhaps something along the lines of this:
As Rags considers herself in the mirror, her smile fades for a moment. Her eyes flashing with sadness before her fingertips find the fabric of her sundress. Her expression softening again after a moment as her fingers softly trace over her curves.
Uses more common language, and while admittedly longer would flow better in the scene. Whilst also better hinting at her past trauma without shattering immersion due to sentence issues, wrong word form and other issues.
Berwyn is an exception because he was a companion. Companions are required to have constant support, and he had a questline that was left dangling, so the fact that his original writer was gone meant that either some other writer was going to be required to take him up and fully support him, or that he had to be removed from being a companion. I believed that it would be the full support, but it seems to have been the latter. They didn't want to force someone to write two companions, and it seems that nobody who was eligible for having a companion wanted to take him as one, so, he was removed from the companions.
Got to admit his companion support being pulled surprised me. Personally I'd have left his companion support in there and moved a key item needed for the main quest into his quest line that player's have to recover. That way he could have organically lost companion support following quest events and would effectively be an Act I only companion, until such a time as support is added back.