Louise, apparently whoever scanned the harp part into the imslip website made a mistake. I went to the site twice: the first visit, HARP part was listed, as having 2 pages, but they were both the same, as you discovered. So I downloaded the PIANO AND CONDUCTOR part 6 pages. You will notice that your first page of the harp part is the same as what the piano is expected to play, up until all those rests where the piano continues but the harp does not. Your printed harp part stops at the change of key to 2 sharps, right? At that point (measure 85, molto meno) I believe the harp continues, just as the piano part does. My advice unless you can find a perfect harp orchestral part to the Monti elsewhere, is to download all 6 pages (marked pages 2 through 7) of that PIANO AND CONDUCTOR part, enlarge for easier reading, and first number all the measures, out in the margin. Then do not practice all the Allegro Vivace and Allegretto measures ; that begin at measure 113 and continue until the end of the piece. Just play the concluding last two measures with the rest of the orchestra.
The second time I looked for the HARP part on the imslip website, it had vanished!! I think someone reported that mistake, and that part was removed.
To sum up, once you have downloaded all 6 pages of that PIANO AND CONDUCTOR part, (166 measures), the harp would just need to play: measures 1 through 21; 86 through 117; and possibly measures 165 and 166. Best of luck!!