I see what you're saying, but I think the issue is beyond that.
It's the fault of the sharer for, obviously, sharing it to a minor. Directly speaking, it's this persons fault. Without this guy, a minor would never be involved and see it. In a best case scenario, this guy never exists and the images stay between consenting parties and adults.
It's Claire's fault for the root cause and she is to blame for the actual act. This isn't really fair to place squarely on her, as what she did is technically fine in all regards. People sell nudes all the time. So why is there an issue?
The issue lies in where she is selling it and the context of the place she is in. It's not like she's selling it in a community meant for it like a porn subreddit or a 18+ discord. She's selling it on a video game Star Wars server that she knows has lots of minors, many of whom have likely interacted with her in other contexts like roleplay. No matter how safe you are and how much you confirm you're selling to an adult who you trust, there is literally no way you can make sure it doesn't get out and to a minor. I am sure if she continued to sell that it would have happened.
How could you sell pictures like that and not at all think that these pictures could get leaked and shown to a minor? Especially if it continued, which (correct me if I am wrong) is likely what would have happened if she wasn't banned? These pictures would one day be leaked and would be seen by a minor and that is clear to see. Thats where the problem is for me - the willingness to do something that is obviously wrong for some extra money on the side.
TL;DR
Selling porn not a big deal to adults. Selling porn on community with tons of minors and no real security that they wouldn't see it is a big deal. Obviously not the right place for it