Yes, although it is not all that rare for a girl to win a junior fell race, the numbers of runners are rather small, so it does just need a top girl to be in a field where none of the top boys are running (which also applies to all the senior examples mentioned in this thread). But it was very striking to see that video from Coniston Gullies with five girls coming past before the first boy appeared.
One thing that is very noticeable in results lists of junior races is how numbers of boys and girls are roughly equal in the younger age groups, with the proportion of girls then falling off as you go up the age range.