The 29-year-old Manipuri, who would be returning without a medal from the mega-event for the first time since its inception in 2001, made the cut after her quarterfinal nemesis Nicola Adams of England defeated Russia's Elena Savelyeva 11-6 in the semifinals today.
"Olympic slot confirmed finally! I am so happy," the mother-of-two told PTI.
"I saw the bout. I know the Russian was not very good but I am a bit sad as well because I won't have a medal around my neck this time," added the reigning Asian champion.
"Medal is very important for me. I am happy with the qualification but I am very upset not to get a medal."
Women's boxing will make its Olympic debut in London in three weight categories -- 51kg, 60kg and 75kg -- and the ongoing world championships are the first and the only qualifying event for the quadrennial extravaganza.
In Mary Kom's division, one slot had been taken by China's Asian Games gold-medallist Ren Cancan, who is in final now.
The other slot was to be decided between Mary Kom and North Korea's Hye Kim. While Mary Kom had lost to world number two Adams, Kim had gone down to Savelyeva in the quarterfinals.
The winner of the Savelyeva-Adams bout was to decide the second slot for Asia and luckily for the Indian, the result went her way.
"I was not tense before today's bout. There was no point in worrying about something that was not in my hands. I only thought about god. God has seen my struggle and I knew my hard work would not go waste just because of one loss," she said.
