Well, not only is spider girl 1 year older, but spider people in general are naturally more inclined to hunting, so she has been training in that way longer than the mc, actually in a past chapter she mentions she helps the adults when there's not enough people, so it's likely she has been training her entire life.
They seem to be changing some stuff compared to the novel, in it the kidnapping happened during a festival. Normally there weren't many outsiders around.