Yes, she is reasoning correct, because:
6 1/4 and 2 3/4 are mixed fractions and you can substract them as it shown below:
1. You must substract the fractional parts (which are: 1/4 and 3/4) of the mixed fractions. You can notice that the have the same denominator "4", so you only need write this denominaro and substract the numerators:
= (1-3)/4=-2/4
When you simplify the result, you obtain:
=-1/2
Now, you must sum the integer parts:
6-2=4
Finally, you obtain:
4 -1/2
