Assuming this is based on the rejecter being someone the OC actively likes:

Yorra pre-zeph: Absolute Mental Breakdown

Yorra post-zeph: like a 3. Not that she'd have the emotional capacity to be vulnerable enough to ask at that point XD (but Emille refusing to jump her at first does leave her somewhat perplexed)

Didier: High 6. Offended that someone would reject him but after a good simmer he'll stomp off and leave them alone cos he's still OK enough to respect their decision.

Nettles a solid 2. She can be afraid of rejection, but generally if shes rejected then whatever. she got the thought off her mind, and can return to her work.
Weiss is about the same as Nettle
Orchids about a 5? She doesnt handle it well, but she'll get over it fairly fast
Astras like a 4, doesnt handle it all that well but forgive and forget or whatever. Shes already spent liek a decade pining

Visi is a 10, after a rejection he begins questioning his own worth and takes it really personally

I'd say a 3. It definitely stings her but nothing that a bunch of work can fix.

All of them are honestly a 1, the most emotional being Hiroto and Jacques who could maybe go to 3 or 4

Mmm the highest is a 3 but usually responds with a 1!!

Balei - 2, she'll be a lil sad but not for long, she's got other things to worry about like what's her next lesson plan
Fausto - 8, he'll act like it didn't bother him but he'll be thinking abut for about a week
Yuma - 5, They'll be sad for awhile, but with the right comfort food and movies they'll be fine

Estella is an 8. She's so full of herself lmao the idea of being rejected just shortcircuits her. She won't lose her cool in public but she'd definitely get hit hard by it in private.

Everyone else is uhhh more mature. Heather has way too massive a following and too many suitors to let it bother her. Same with Lex. Lionel is more likely to do the rejecting than anything else. Shayla's too chill to be bothered.

ophelia: depends on who it is! if it's something simple, probably a 2 or 3. But if it's something more serious, more like a 6. even so, ophelia's pretty cool-headed, and she takes rejection very well.

penelope: on the other hand, penelope's perfectionist attitude lands her anywhere from a 6-10. again, its situational, but she's much more likely to get hung up on little things than ophelia. if she doesn't happen to win something over, penelope's gonna be upset about it.

Joltenne: "Oh....I see. Well, it's fine I guess proceeds to get into her work util the sad passes - 4/10
Kaito: "Sigh, I understand. I have seen so many people come and go. It's just natural that my precense puts someone at unease..." 2/10
Sabi: "How can I be good at turning heads yet so bad at dating... drinks a whle bottle by herself" - 5/10
Andreas: "O my love has been rejected againg...well, someday I'll get my chance!" - 6/10
Icebella: *piercing glare *How DARE you. You're not suppose to reject me; I should be the one to reject YOU" 9/10

Elio handles it rather well, honestly, since he's very understanding and knows when to back away. Also, the phrase "there's plenty of fish in the sea" and all that jizz. It hurts initially - especially if he was close, so in such instances he may silently cry here and there, and would require some space to sort things out, but he gets over it fairly quickly. Mainly because of how well he can keep his emotions in check and being naturally optimistic. In the end, he still wants others to be happy, so if breaking up can lead to that form of happiness, all the power to them.

Odd would probably be pretty mellow at a 2 or 3. They'd be perfect cordial in the moment and respect the other/not press for anything, but later when they're by themselves he might get a bit down on himself and have to a deal with a fresh spiral of "I'm unlikeable" thoughts.

They don't need to worry about stuff like this, but before they were together Jin was a solid 1. But this was mostly cuz she was pretty romantically guarded after getting her heart broken in a like level 7-8 rejection :,D And Mary didn't really think about relationships much, but she would've been a 4 I'd say.