The collision happened this morning (credit: DI Brettell)
It happened in Heath Road Chadwell St Mary at around 10.40am today.
Her injuries have been described as potentially life-threatening.
Police are appealing for witnesses to the collision and the moments leading up to it to come forward and help their investigation.
If you saw anything, have any CCTV or dash cam footage, or have any other information, then call Essex Police on 101 quoting incident 329 of 28 January or Crimestoppers anonymously on 0800 555 111.
Tags: Grays, Thurrock, Orsett, Chadwell St Mary