Break the Cutie: The plot pretty much bends over to try breaking the little girl. And it's very, VERY close to succeed. But she pulls through more than once.
Childhood Friend Romance: With Lundi. However, it's less about them being together and more about them staying together through their hardships.
Despair Event Horizon: She's in the border twice. First, when Lundi disappears and it's believed that he kicked it; later, when she willingly decides to leave to save Lundi and her family from Toulonchamp.
Subverted: Jeudi steps on Mathilda trying to kiss him and Lundi attempting to refuse her advances, but she doesn't even think that he's cheating. Specially because Jeudi's concerns in regards to Mathilda areVERYdifferent.
Played straight: she almost has an Heroic BSOD when she sees Mathilda kissing Lundi. To be fair, not only Jeudi saw them from a distance so she couldn't exactly see that it was more of a Forceful Kissand she was still BSOD'ing after almost being killed.
Chekhov's Gunman: The only word Printemps can say is Alpine Rose. When he says them in front of Helene...
Evil Detecting Bird: He once attacks Mathilda during breakfast. Mathilda immediately lampshades the trope via angrily asking Jeudi if Printempts thinks she's a bad person. (And actually, he was right: Jeudi's tea was poisoned, and Mathilda is the one who did it)
Loving a Shadow: His first and eternal love was a girl named Helene. He chases Jeudi around because she's identical to her (and is her child but he doesn't know it), so she reminds him of the woman he loved but couldn't have.
Childhood Friend Romance: He's in love with Jeudi, but she doesn't return his feelings and she ultimately chooses to stay with Lundi.
Elegant Classical Musician: An accomplished pianist. And it plays an important role as it comes out in handy when he uses an anti-Nazi song in his "Austrian symphony" to escape from the Nazis with Jeudi.
Chekhov's Gunman: She's the woman who rejected Germont's love in the past. And Germont later finds her daughter Alicia/Jeudi and also chases after her, specifically because she looks like Helene. (Though he won't know who she really is until much later.)
Ill Girl: Has a weak heart and almost non-existent eyesight. What makes this worse is that Mathilda and her father have been slowly poisoning her for a long time, so they an keep her physically weakened enough to mantain the masquerade.
Aristocrats Are Evil: Toyed with. Mrs. Durant is a sweet person and immediately recognizes Jeudi despite not being able to take her to Helene, but Mr. Durant is much harsher due to the massive stress of the Toulonchamps being on his tailand having to face the huge consequences of having separated Helene and Friederich.
Heroic BSOD: Mr. Durant suffers one when he finds out that Jeudi almost died and that Helene has been slowly poisoned. Then he has another (and quite more serious) when Toulonchamp makes clear that the family is totally in his hands.
Impoverished Patrician: They were very noble and rich, now they're still very noble but they're squeezed and manipulated by Toulonchamp.
Kick the Dog: Mr. Durant, when he accuses Jeudi of being in cahoots with Friederich and starts insulting the dead Brandel's memories. Jeudi's reaction is smacking him.
Fille Fatale: Throws herself at Lundi, only to be rejected every single time. (At least in one of them she got to plant him a Forceful Kiss.)
High Heel-Face Turn: Averted. She hates Jeudi but willingly reveals her true nature as well as her heritage to Lundi, saying she's doing so specifically because she has taken a liking to him. (Her other reason is that Anna's huge blunder scared the crap out of her.) However, this doesn't mean she will leave her father's side...
Master Poisoner: While it's almost impossible to have her as a proper poison maker due to her extreme youth, Mathilda is still sly enough to slooooowly administer it to Helene to make her ill. She's also all but stated to have poisoned Jeudi's food, but she didn't get to finish the work.
Batman Gambit: He uses his youngest daughter Mathilda as Jeudi's Body Double, having her trick Helene into believing she is the real Jeudi - which was very easy back then, considering that Helene's non-existant eyesight doesn't let her see that Mathilda looks nothing like the grown-up Jeudi, who has been missing for a long time so nobody really knows how she would look like. Then, once Mathilda has wormed her place in Helene's affections, he black mails the Durants into doing whatever he asks them too, threatening with taking Mathilda aka the fake!Jeudi away from Helene - which will be fatal for Helene due to her Break the Cutie past and her very weakheart. (Oh, and in the manga there's the small fact that he has been slooooowly poisoning her)
The Maid Did It: She is an accomplice of the Toulonchamps and once drops a flower pot on Jeudi's head from the second store to try silencing her; Jeudi jumps out of the way but she still hurts her foot.
Meido: She works as a maid in the Durant home. And as the Toulonchamps's spy and partner-in-crime.
Nice Job Fixing It, Villain - Spanner in the Works: In the manga, she tries to kill Jeudi but fails. This starts to plant the seeds of doubt in Helene's mind, helps uncover the deal with the poison and scares Matilda enough to tell Lundi who the heck she truly is...