To find Rachel's unit rate, we divide the distance she travelled by the time she took:
Rachel's unit rate = 45 miles / 4.5 hours = 10 miles per hour
Eleanor's speed was given as 10.5 miles per hour.
Comparing the two speeds, we see that Eleanor was riding faster with a speed of 10.5 miles per hour compared to Rachel's speed of 10 miles per hour.
Therefore, the correct answer is D. 10.2 miles per hour, Eleanor was faster.