She might not even have known that there is a different way of doing it. The guild had to tell her that she was owed money and benefits. That's different from taking somebody else's place. There is probably no entry process for newcomers to lean about better way, since it is not a company but a nebulous industry with thousands of independent actors in the game. That's why the guild is necessary, it's impossible to expect each new excited, clueless person with an idea to know and bargain for that on their own.

The problem will persist as long as the exploiters can do it. You will never get every person to individually negotiate the right way.

Game developers should also unionize at industry level. That way new developers would be protected right away and could not be exploited before they realize it. No need to dissuade them, although there probably will not be that many openings that often anymore.