Alternative original solution:
Sarah's deck consists of two mountebanks. Her opponent receives 2 coppers and the last curse. Unfortunately for Sarah, her opponent has 8 gardens and 8 fairgrounds with 37 cards in deck and no coppers or curses. More unfortunely, her opponent has 13 unique cards. This results in a +23 swing for her opponent. Even after buying a colony, Sarah loses by 14 points.
Alternative qualified solution (has to win better with just golem play, not KC/golem).
requires Sarah choose the order of which card to play (either order is fine):
Sarah's deck consists of remake and mountebank. Sarah pitches two plats. Unfortunately, this leaves her with 38 total cards. Each of the 8 gardens on her native village mat is now worth one less. Sarah gives her opponent the last curse and a copper, but unfortunately for her this makes each of her opponent's 2 fairgrounds worth 2 additional VP.
If Sarah buys a colony her net gain is -8 from gardens (she has 39 cards), +10 from colony, +1 from curse, -1 from starting VP, and -4 from fairgrounds. Net, Sarah loses by 2.
Had Sarah played just the golem, she could have remade her KC into a province and bought a colony. This latter course would have resulted in +0 from gardens (she has 40 cards), +6 from province, +10 from colony, +1 curse, -1 from starting VP and -4 from fairgrounds. Net, Sarah wins by 12.
requires nothing (just VERY contrived):
Sarah's deck consists of two upgrades. Sarah trashes two plats leaving her with 28 cards which unfortunately lowers the value of each of her 8 gardens (safely hidden in NV mat - the NV was islanded away) by 1 point. This leaves Sarah down by 9. She cannot overcome this with a colony as the colonies has been embargoed 10 times. Most unfortunately for Sarah all the other piles in the game (including treasure & victory cards) have only 1 card left in them.
If Sarah buys the last Colony she ends the game with 39 cards. From the start of her turn she has had no net change in her garden value, but has had +10 from the colony and -10 from the curses. This leaves Sarah 1 point short.
If Sarah buys the last province she ends the game with 29 cards. From the start of her turn she lost 8 points in garden value and gained 6 points from the province. Sarah loses by 3.
Had Sarah played just the golem, she could have upgraded her KC into a province, trashed a plat & bought a duchy. This leaves her with 30 cards & no change in garden points while gaining 6 from the province and 3 from the duchy. Sarah wins by 8.