Hi costicina,
First, for a 12 year old student to be able to get so far in this piece is remarkable. So my compliments on that!
You made an important observation in a prior message above--fluidity. Not that it's bad, for it's actually good, but it could still be even a little better. A couple of suggestions:
As to balancing the hands, think of the melody as always being in the foreground, while the accompaniment is kept in the background. So two levels of sound, not including voicing of double notes and chords. Another way to put this is that the accompaniment needs to be generally quieter and should never compete with the melody which must soar over the accompaniment.
The other practical suggestion would be to recall that for every performance, there need to be a certain number of practice iterations that varies by pianist. This fosters solid articulation and confidence in the playing. For example, it might be a ratio of four practice runs to one performance. Your daughter will already have a sense as to what that is in her own case. Where there are many intricacies in this piece including the shifting from natural keys onto black keys, slow and somewhat mechanical practice can iron out wrinkles very nicely. If there is place or a few that are especially difficult, those can be isolated for more intensive practice. The mechanical practice will then facilitate artistic performance. But sometimes even that not sufficient. Using the actual motions used during performance in practice iterations can also help solidify results.
Sometimes in her playing, for instance in executing a leap, there is that small hesitation of uncertainty and worry that breaks the fluidity. First, she can use the metronome to discover the weakest places in the music where continuity loses momentum. So it's extremely helpful to play through the piece a couple of times with the metronome. (The objective is not to play metronomically, but instead to use the metronome simply as a tool to discover hesitations interrupting the tempo.) She can then mark those measures for more intensive practice to ensure that the hands are correographed to best advantage, fingering is most effective, the hands "know" their notes and rhythms, and very importantly that she can be anticipatory in meeting the more difficult technical demands as they arise in performance.
By the way, I've always been impressed by the Michelangeli recording of this intermezzo.
I hope this helps.
P.S. My birthday is the 29th, so how well I know the Christmas/birthday situation.

David