]You have probably heard of early 1810s' landscape designer Capability Brown whose idealized garden features includued green slopes, hyacinth dells, and temples near lakes-so refined and amicable!

Yes, he's one of the people whose work is described on the page I linked to, above.

]Around 1810 ( Am I right the date of 'S&S' isn't certain?)

It was published in 1811, although the first version of it was written in the late 1790s, and I have read a calendar for it, explaining how the dates could work with the years 1797 (death of Mr. Dashwood in February) through 1798 and beyond.

However, JA also supposedly added details to it before it was published, and it is thought she actually rewrote the whole thing, changing it from letter form to its novel form.

] At this point in time perhaps the fashionable Palmers were in the middle of their new garden renovations.

It sounded to me like it was all new, with their 'modern-built' house, plus they have only been married for one to two years.

]Wandering about like a moonstruck mouse seeking solitary peace she wandered the soothing geen slopes of the idealized landscape-no doubt mumbling poetry to calm herself! Yet 'torn asunder' by her heart, she swung back to wild grief and rambled further to the wilderness that matched her mood. Perhaps the cold that became a fever signified an emotional breakdown.