It was on speaker and she knew Clarissa was there. Clarissa said it didn't sound like a joking voice. Charles is also known to think the best of other people
It sounds to me more like Clarissa may be trying to think the worst of other people! On the bolded, since she doesn't know Daphne that well, how would she even know what her joking voice sounds like?
I wonder if Clarissa has recieved unambiguosly negative comments about her ring from other people, and is therefore somewhat sensitive, and is maybe thinking "the worst" of Daphne because of that, maybe just assuming, without really thinking about why, that Daphne also means to put down the ring or even the whole relationship
It wouldn't be fair if that is the case-not fair for others to put down anything about Clarissa's relationship
or ring, and not fair for Clarissa to jump to any conclusions while hardly knowing Daphne-but it would be totally understandable if Clarissa's sensitive reaction is motivated by this, I think, and I hope that eventually the ice can get broken and she and Daphne can be comfortable together, because, like most posters, I am 99% sure this was just a joke-and even if it wasn't, I agree with the posters who have said it would be best for Clarissa to act as though it were, at least for now, unless/until other evidence turns up.