Commentary Par XXX 19-21

Dante will see Beatrice once more, after she resumes her seat in the Rose (from which she arose once, on 24 March 1300 [also Maundy Thursday according to Dante's Idealized Earth Time], in order to draw Virgil forth from Limbo; and then again, around noon the following Wednesday, in order to descend to the earthly paradise for her reunion with Dante).  This, however, is his last attempt to describe her beauty, which has been increasing from his second description of it (in the heaven of the Moon, [Par IV 139-142]) every time he sees her anew until now.  That this 'program' has come to its end is clear from the seven tercets ([Par XXX 16-36]) devoted to a final description of her increased beauty, which offer a kind of history (esp. vv. 28-33) of that beauty's effect on Dante.

On the point of returning to her undivided attention to God, she is already being retransformed into a more-than-human being, pure soul, as it were, without the hindrance of human concerns that she has taken on for Dante's sake.  Thus only God can fully enjoy her beauty.