She never said this.
It does seem to be a bit of a twist on her words
http://abcnews.go.com/blogs/politics/2011/11/us-embassy-in-iran-michele-bachmanns-oops-moment/
According to reports, Bachmann applauded the U.K.’s move, adding, “That’s exactly what I would do [if I were president]. We wouldn’t have an embassy in Iran. I wouldn’t allow that to be there.”
Where does she say we have one? She just said she wouldn't allow one.