You know the first time I read this I thought Sugi was just an asshole always denying that what they shared is really love, but now I see that it's more like she thought that they were just friends that were confusing friendship with love and was worried they'd just hurt each other or waste their time trying it out of pity or whatever, she also seems to know that the path they'd need to take would be filled with hardships and wants to keep them away from it.
But the moment she sees that Akko is very serious about it she just drops the whole thing and genuinely cheers her on and is happy for her, even giving her advice and tells her to stop fucking around (thank God).
Also i like that she's really sharp, instantly was on point with what Akko was talking about, I fucking hate it when friends don't realize at all even though they call themselves friends (looking at you Hana ni Arashi) so I appreciate that Sugi is so sharp.
She may be a slut but she really is the most mature.