Dorothea and Celia are very different, and thus Celia’s opposition to Dorothea’s marriage could be interpreted as a simple clash between their ideals. It would not be good for Dorothea to marry someone who Celia thinks is a perfect match. At the same time, the intensity of Celia’s sadness is foreboding. She may not be the same as Dorothea, but she knows her well, and thus might be right in predicting that Dorothea will not be happy with Casaubon.