The 29-year-old mother had to rest content with a bronze.
The Briton will take on Ren Cancan of China in the final.
Five-time World champion Mary Kom was no match for her British opponent, who was egged on by a vociferous home crowd that included Prime Minister David Cameron [ Images ] and last edition's silver medallist Aamir Khan [ Images ].
Nicola Adams (Britain) beat Chungneijang Mery Hmangte (India) 11-6
Ren Cancan (China) beat Marlen Esparza (US) 10-8