"We despise those traits in others that we ourselves so often exhibit."

I actually don't think that Marianne and Mrs. Jennings have so very much in common, beyond being both very animated and desirous of the felicity of others. Mrs. Jennings is much more obtrusive, though a kind lady, she's very trying. Marianne tends to stay in her own circle. I actually excuse Marianne her presumptions, because she is in the company of Elinor every day, whereas Mrs. Jennings makes *her* assumptions after seeing Marianne and Col. Brandon a few short hours, a few short days.

Also, Marianne dropped the subject after Elinor disabused her of the idea; Mrs. Jennings persists with her notions in a manner that offends.