I've never bought from Ralph Lauren before but have seen a coat that I love. I'm short so have to get petite, but they only have size 8. Of course there's a size guide, but I never trust them! I always go for petite but depending on the shop I can be anywhere from a size 4 to a size 10!!
The coat in question if anyone has it and can tell me what the sizing is like - https://www.ralphlauren.co.uk/en/water-repellent-belted-twill-trench-coat-100005869.html#start=1&cgid=women-lauren-petite