Is the answer 8? If so, what is the unit?

Step-by-step explanation:
that depends on the expected unit rate.
there are infinite correct answers to this as it is stated. including the initial numbers.
2 miles in 0.25 hours is by itself already a unit rate :
2 m/0.25h
but if we want it to be the classical miles per hour rate for speed, then we need to calculate how many miles she would have run with the same speed in 1 hour.
when we change the denominator of a fraction or ratio by multiplication, but want to keep the overall value of the fraction unchanged, then we need to apply the same factor also to the numerator.
what is the factor for 0.25 hours to create 1 hour ?
you know that 0.25 = 1/4.
0.25 × f = 1
f = 1/0.25 = 1 / 1/4 = 4
we need to multiply by 4 to get 1 hour as denominator.
therefore, by keeping the ratio value unchanged, the whole operation is then
2 m/0.25h × 4/4 = 8 m/1 hour = 8 m/h
the answer is therefore only 8, if we required mph or m/h as unit rate.
we could just as easily request "miles / 10 hours", and we would get 80 as answer. or 0.13 as per 0.13 miles/minute. and so on. infinite possibilities.
you see ? the question in that form is actually not complete.