Wait, that's actually a good question.
So Marinette and Adrien don't put two and two together on Dawn being Chloe's kid until they have a little meet the parents pow-wow when Dawn is invited to a sleepover or something. In their defense, it's not like Emma would be saying much about her crush's mom when she's dreamily rambling about this awesome new friend she made at school, and what few details she drops are obscured by Chloe being y'know. Much older and post therapy with a law degree and a new last name.
Emma however, is a Dupain-Cheng, so does Chloe put it together any sooner than Adrien and Marinette do?
My assumption is that she figures it out like a day or two before them when Dawn asks to sleep over, and Chloe says yes, but she'd like to meet Emma's parents first and Dawn says something along the lines of "Oh yeah, here I think Mr. Dupain-Cheng gave me his number the last time we stopped there after school," and Chloe chokes on her spit.
Which means there is a pretty large space of interactions Chloe and Emma can have before either of them know there's a history there. Like if Dawn brings Emma by the hotel to hang out after school several times. And I'm just cackling imagining the first time they meet is like:
Emma, internally: Oh shit this is Dawn's mom, Dawn is super close with her mom, I have gotta make a good impression
Chloe: Hello child that does not live here
Emma: *incomprehensible stuttering because she IS Marinette's child*
Dawn: Mom! This is my new friend from school I was telling you about! Emma! I was just showing her around
Chloe: In the boiler room?
Emma: *Keyword recognized, unskippable dialogue activated*
Emma: Mlle Mellifera, are you aware your hot water heater has a slow leak?
Chloe internally: Ah. Neurodivergent pack bonding
Chloe: You know, for once I WAS actually aware of that, but I am fascinated to know how a 14 year old figured that out when I didn't even notice anything until I called a plumber to check things out on principle. After you have to call the 4th expert to fix a new and exciting problem caused by 20 years of neglect, you start to get paranoid and just check everything.
Emma internally: Nailed it
YEAH IT.
Chloé def figures it out first and she like.
She doesn't think it'll be that big of a problem. Like she's chilled out and will probably just have to make a 'sorry for being an ass' conversation and they can be mature adults and ignore petty middle school drama in favor of their kids' friendship.
She has no idea about Marinette being Ladybug or the paranoia of the current Butterfly and all that.
