You mean it? [ It's not that she doubts Kohran's sincerity, but she did say "that bad"; implying it was even still a little bad.
Though, really, if she doesn't get it drilled into her thick skull, Subaru can be kind of oblivious to signals, so she catches no intent in her own words, much less when her friend says she wants to get to know her in return.
She takes her friends hand in both of hers, beaming wide. ] Mm! I'm happy to have your forgiveness, Kohran. I won't let something like that happen without your permission ever again! I promise!