Aileen Whelan found herself in acres of space in the box and fired home past goalkeeper Ann-Katrin Berger to give the home side the lead heading into half-time.
Chelsea came out stronger in the second half and were rewarded with James’ equaliser, despite the controversial circumstances surrounding the goal.
The draw leaves Chelsea still unbeaten in the Women’s Super League this season, but they will be disappointed not to have taken all three points against a tough Brighton side.