It's probably because of her age and the school schedule. If I give a test of that nature to a small child, I monitor attention, energy level, and engagement pretty closely, and definitely have broken up testing into multiple sessions in response to their individual needs.
Also, if pulling a child out of kindergarten class time to do this, one sometimes has to work around constraints such as pulling them only from specials (gym, art, music), because teachers don't like missing instructional time, or, conversely, pulling them only from not-specials, because students don't like missing them, and won't give optimal performance under those circumstances. For example, a typical situation is that you can't take them from opening or closing circle time (so that's about 40-60 minutes of untouchable time there), or from the special of the day (another 30 minutes), or from snack (15 minutes). And, of course, the remaining time isn't necessarily contiguous. Especially if this is a two-and-a-half-hour half-day kindergarten, that makes it pretty difficult to complete testing in a single day.
Another practical consideration is the other cases already on the list ahead of her, who have due process clocks ticking. By law, the school psych may have to do those first (depending on where their deadlines fall), which may account for some of the two weeks.
This is all more detail than you probably need, but suffice it to say that, no, there is nothing odd about breaking up testing into two weeks of short sessions!
