Vijeta Devi opened the scoring for Delhi in the 14th minute of the first half.
Sikkim equalised in the 24th minute through Mondmit Lepcha. The winning goal from Delhi was scored by Poornima in the 54th minute of the second half.
Delhi have won all their four matches in group C cluster and lead the group with 12 points. The last match of the group will be played against Kerela on May 5.