Despite national catastrophe in Spain and her complaint on their dreary weather, the tone of Jane's letter comes across to me as cheerful and teazing of family and friends, including Cassandra.
Letters from her seafaring brothers, Charles and Frank may have put her in a buoyant mood. Jane had also been well entertained at a Ball.
Interestingly, Jane also mentions her Mother talking to Eliza about our future home. When writing this letter to Cass. Jane may've felt happy at the promise of a new home.