Findmypast has overseas marriages from 1765. I am not a member so cannot access it for you but someone on here may well be able to.
I sounds as though, if you Aunt went out to work in India she possibly married out there.
Her husband being District Commissioner may have been military so military weddings are a possibility - again FindMyPast.
If she is listed (and you say you don't know her ?surname, it should still be possible to find her by looking for her husband's name in marriage records and noting whether he married an Edith. His initials being C S he is almost certainly a Charles/Cecil/Christopher I imagine.
Sue