You're totally right. And there definitely is a historical context to this.
Still, I do feel bothered by Simon's anger. He knew what she was before he got engaged and he fell for her anyways. I think he's expecting her to change and become reasonable and I think she just isn't capable of that. He doesn't try to see things her way. Like in this episode, what did she do to deserve his ire. Yes, she's dressed like a maid but that's not detrimental to her health or safety.
And she didn't meet up with the thief on purpose either. It was forced upon her. He's the one chasing her and not the reverse. She also didn't put herself in a position of danger as she used to. She's just being herself.
It's not that I don't get where he's coming from but I kinda fell out of love with this character because of it.
I understand why Simeon is pissed off at Mareille. She's hanging out alone with a notorious villain that has outright stated that he has romantic interest in her while she has a fiance. If anything, Simeon has been rather free in letting her do what she wants. He let's her hangout with prostitutes and tag along with her investigations for her writings. It was stated at the beginning of this series that most men would have wanted to drop her eccentricities. Simeon just doesn't want her to associate a known dangerous criminal that has outright stated to BOTH of them that he wants to kidnap her because he knows how reckless she is. She is the kind of person who would throw away common sense and tag along with someone dangerous when there is an interesting story. Lutin is that interesting story but one that has the ability to successfully kidnap her.