agreed, 義母 or anything with the word 義 on it is simply means 'not blood related', so it can be a mother-in-law, foster mother, or stepmother. In this case it would be stepmother as you said.Just a heads up: "義母" was translated as "mother-in-law" on page 19, but it can also be read as "stepmother" which makes more sense contextually.
The villainess term doesn't describe Sofia, it describes Sofia's stepdaughter Rebecca.>Title causally adding in the 'villainess' term despite nothing in the story's setting lends any credence that Sofia would earn that moniker
I think you're right, I'll see if I can change it.Just a heads up: "義母" was translated as "mother-in-law" on page 19, but it can also be read as "stepmother" which makes more sense contextually.