The island is huge, 70 miles East-West and 90 miles North-South. If you've seen islands on inland lakes, on the Great Lakes, or off the Atlantic or Pacific coast, you're thinking too small. As long as you're not standing on the summit of Pike's Peak (or Mauna Loa), you're probably unable to see beyond the curvature of the earth to a horizon comparable to the distance from the caldera to where your friend lives, and the probability that a lava flow oozes all the way to the horizon is vanishingly remote.
However, the bigger factor in your friend's safety is that the vast majority of the population live near the coasts of the island, very very very few live near the peaks. Also, 5x as many people live on the 5x smaller island of Oahu in the city of Honolulu rather than on the island of Hawaii...if your friend lives "in Hawaii", statistically they probably live on an island 200 miles away, or potentially on the coast 40+ miles from the summit, it's extremely unlikely that a random Hawaiian lives on the slopes of Mauna Loa.
There are a number of islands in the Hawaiian Islands spread over a fairly large area. (For commercial travel, you need to fly between them.) The biggest, where the eruption is happening, is also called Hawaii although locals refer to it as Big Island unless they're referring to the state as a whole. Big Island is 4,028 square miles (10,430 km2) and has a population of about 200,000 most of which is on either the east or the west coast.
Most of the population of the state though is in Honolulu on Oahu (also where Pearl Harbor is). There are over 100 islands but just 8 main ones of which casual visitors might visit 5.
However, the bigger factor in your friend's safety is that the vast majority of the population live near the coasts of the island, very very very few live near the peaks. Also, 5x as many people live on the 5x smaller island of Oahu in the city of Honolulu rather than on the island of Hawaii...if your friend lives "in Hawaii", statistically they probably live on an island 200 miles away, or potentially on the coast 40+ miles from the summit, it's extremely unlikely that a random Hawaiian lives on the slopes of Mauna Loa.