That difference is not ontological. The difference is that her baptism and sanctification occurred earlier than for the rest of the saints. The superlatives in the encyclical refer to the superabundant merits of Christ and should not be a source of any controversy.
"The superlatives in the encyclical refer to the superabundant merits of Christ and should not be a source of any controversy."
Actually, that concept (superabundant merits of Christ) might be a source of great controversy, Alex. For example, how does God have a "superabundance" of His own uncreated energies? :)