I think she did it herself. There has been massive speculation that Blair has secretly converted, maybe this is her way of letting the Pope know.
IIRC, under British law, Blair cannot remain PM if he is not a member of the Church of England, but I may be wrong about that. I do know his children are Catholic and that a Catholic priest says mass for his family which he attends every week. It would not surprise me if he does convert. However, if his wife wanted to let the Holy Father know that he had converted, why not just tell him.
Don't seem to be much speculation here about Cherie's attempt to convert Tony ...I guess nobody cares that much.