Wanted to document this for posterity...
The first time Yordi said "Oh my God!" I looked at Lee and said "Did you hear that?" He said, "Well, she didn't get it from us!"
The problem is that it's so totally cute (she says it like "Oh my gawt!") ... um, ahem... and so inappropriate. So we started saying "Oh my Goodness." every time she said it. We didn't tell her not to say it.
Today she said "Oh my goodness."
Then Habtamu said "Oh my God."