check out Knoydart, Scotland. It’s located between Loch Nevis and Loch Hourn and is only accessible by boat or foot. Knoydart is famous for its rugged beauty and tranquility, making it a popular destination for hikers, mountaineers, and those seeking a getaway from urban life. not sure if this would be a fit distance-wise to your sister’s place but….
Alexandra Ross Works 
check out Knoydart, Scotland. It’s located between Loch Nevis and Loch Hourn and is only accessible by boat or foot. Knoydart is famous for its rugged beauty and tranquility, making it a popular destination for hikers, mountaineers, and those seeking a getaway from urban life. not sure if this would be a fit distance-wise to your sister’s place but….