You really need to end the idea in your head that refusing to engage in any conversation about this is "lying for them". There's a difference and you need to realize it. Saying that it's not your business or that the gossiper needs to talk directly to the couple is not lying. In fact, it is the truth.
I think this is a very good point.
"No, they didn't get married" is a lie. "You'll have to ask Candy about that" is not. "Yes, they did. I was at the wedding" means that you aren't willing to keep the information quiet, and should warn Candy about that.
Personally, I think Candy's quest is doomed to failure. I can understand why she doesn't want to open themselves up to the kind of ridicule they are likely to get at the office, but given the circumstances and the gossipy nature of the office, I don't think there is any chance.
But the key is that you don't want to be one of the gossip vectors. If people go to Candy and say that Alias told them she and BF got married last weekend, then she will (rightly) know that you are someone who can't be trusted to keep information confidential when asked. And there's a good chance that she will be angry at you, or will drop you from her list of trusted people.
Of course, saying "You'll have to ask Candy about that" basically tells people that there is something to hide (part of the reason I don't think that Candy is going to be able to keep her wedding quiet), but you're not the one who is spilling the beans.