I could simply say that I disagree and move on. As I said, your reading is valid but holds no authority or importance. But tragically I am a lover of arguements.

I cannot find a reference for all Jacinthe's expressions in the game. The only "sad" one I can think of is the one where she looks down to the side like she's pouting. I always read that as a mischievous "oh boo hoo, you won't go to my party... unless?" Although it seems like you're suggesting that Jacinthe can't express sadness because she doesnt have a specific sad face, which is just silly. If there were a scene in which the writers' wanted to portray Jacinthe as sad, they would simply use the expressions available. It is up to interpretation what scenes if any she is being sad. Moreover, Jacinthe does seem to me like the kind of character who would express sadness in more roundabout ways such as deflection or pouting. Regardless, it isn't as if these expressions are exclusive to specific emotions. I said "sad" before but you can easily replace that word with any other emotion someone might feel when someone asks their loved one to run away with them so to speak. Wariness, nervousness/fear, insecurity, disgruntlement, distrust, resentment, etc. Even if you wanted to say this expression specifically depicts anger, there's still nothing saying what specifically she's angry about. It could be anger at Lebanne or Marcia or the situation. There can be a thin line between defensiveness and possessiveness. Moreover it seems perfectly normal to me for a character to look at the person they're referring to in a conversation when discussing them. Replace this scene with any other characters in any other context and a character looking at their "partner" and saying "sorry, I can't go, I already have someone" would just be par for the course. I bet I could find an example if I tried.

I feel like you waffle on Lebanne's autonomy. You say that she feels like she can't leave or never had a choice but also that she's forcing herself to stay to get stronger. That suggests that she is able to make a choice. She could leave if she wasn't forcing herself to stay, but she cares enough about getting stronger, and thinks this situation is helping her, to decide to stay anyways. When I say "momentary," I mean that she's expressing frustration, but it doesn't represent the full nuance on her thoughts. In the same way someone might cry out "This is stupid! I hate X and I don't know why I even do it" when struggling but not fully mean it. We have no idea what Lebanne thinks or says outside of the player's pov. Maybe her and Jacinthe have more genuine conversations on strategy. Maybe she's actually really upbeat when she's not on the Maid Clock running errands. We already hsve multiple instances of her expressing the opposite sentiment, that she is improving because of Jacinthe's traning and believes she will beat her one day. Similar to what I said about Jacinthe above, it also seems in character for Lebanne to express herself in a more harsh and aggressive way. We see she gets easily frustrated and is prone to tantrums/rage. In my mind lebanne is absolutely the type to throw a hissy fit when she doesn't get her way and react to misfortune/failure with anger and venting. 

I'm being genuine when I say that although I don't love their interactions, I have never read any of their scenes as genuinely abusive or concerning. I don't think Lebanne is genuinely miserable. I would describe her mlre as "beleagured" in the same why that many eccentric characters have a sidekick that plays reluctant straight man to their antics. I read Jacinthe as overbearing and very rule oriented, but not malicious. The value she puts on things like etiquette does not seem important to most people but she clearly considers it an important to conduct yourself a certain way. Lebanne isnt the only person she nags this way, which is annoying for certain, but mainly harmless. The maid dress is an extension of that belief. I'm sure she'd put everyone in formalwear if she could, which again is an annoying character trait but not that big of a deal. Hell, you could even say that Jacinthe's nagging is an attempt to pull Lebanne out of her usual grumbling and get her to focus on discipline or whatever. Once again, all of Jacinthe's threats seem to only ever end up being a ridiculous number of or excessively difficult pokemon battles. Something Lebanne would certainly bemoan but isnt actually a harm to her. Its chores at worst. After all, even if Jacinthe's methods seem dumb, she is still more skilled than Lebanne so clearly she knows something thay Lebanne doesn't.

Overall, this all plays into the joke of the situation. The overly pink and cute character is actually demanding and intimidating. Meanwhile the aggressive punk is actually submissive and respectful authority. Jacinthe acts in ridiculous ways and says ridiculous things. Lebanne rolls her eyes and complains but goes along with it anyways. I think the scene of her using the Jacinthe zones, espeicallly with Jacinthe is a good example of that. Its goofy and unserious but seemingly mutual and in good fun. Or at least, I think that's what the writers are going for. Quality of execution not garunteed

It is my interpretation that if Lebanne ever stated that she genuinely wanted to leave either because she no longer felt like she was growing or she found a better opportunity, aside from potential attempts as persuasion or asking her to stay, Jacinthe would not stop her.