An own goal by the Hammers' Katie Longhurst and Jess Sigsworth's second-half strike ensured the Reds ran out 2-0 winners.
This was the Reds' second game back after a three-week festive break and Sunday's 9-0 league win against London Bees was followed up with an equally impressive performance against West Ham.
The first effort of the game came after just a few minutes from full-back Kirsty Smith, but her right-footed shot from outside the area was comfortably saved by West Ham goalkeeper Becky Spencer.
The hosts dominated the early proceedings and nearly took the lead after just nine minutes when Alex Greenwood’s deep cross, aimed for Lauren James, took a nick off a Hammers defender and flashed just inches wide of the far post.