It's pretty normal for both ladies and boys to do the chasing behavior during the breeding season
It really doesn't matter if there's a boy there or not, the goldfish girls will lay eggs anyway when they're ready. There was this case on the forum before where one had a goldfish boy and he spread the milt allover the gravel without there being any eggs or females around

But it might also be that the one chasing is a boy that's simply not mature yet, it's pretty hard to know if you can't see any breeding tubercles on the gill covers.