Both Harriet and DOMW use "pretty" to describe non-human things: the former the Martins' cows, the latter a servant's manners and way of speaking. In both cases, approval is being expressed, but not necessarily appearance -- although DOMW does call Mr Elton "pretty", as well.
It strikes me that the word "pretty" had a slightly different semantic range in JA's time than it does now. Anyone versed on the subject?
Also, I wonder whether the use of (what I'm assuming is) a slightly trite word like "pretty" is intended to characterise the somewhat, erm, limited mindset of both Harriet and DOMW?