Hi there, I currently coach at the D1 level at a fairly large school. A lot of the girls we recruit are in the 4:55-5:00 range for 1600m and 10:30-10:45 range for 3200m. Although they aren't the absolute top girls in the country, they would be considered very good in most states. Because of this, I feel like I can give some good insight on what some good programs have their girls doing for mileage in high school, as well as other things they have in common.
I would say most of these girls, as well as the sub 4:50 and and sub 10:20 girls I've recruited, tend to hover around the 40-50 mpw range. If a girl runs 60+ mpw, I consider that to be quite high when compared to a majority of athletes with similar PRs. Occasionally I run across girls who are achieving fast times in the 25-30 mpw range, but it is less common.
After a while you start to notice that a lot of the top girls all kind of do the same thing. Their training is really uniform. Their coaches have them do a bigger emphasis on tempos over race pace work. They often use races as "workouts," and they do a lot of hills or fast speed work year-round to stay sharp. Many times they do not drop their mileage until the very end. Long runs sometimes varied....some did them and some did not. Almost none of them doubled or ran on Sundays. Many were 6 days a week of 40-50 mpw, so their average single session run was in the 6-8 mile range. You get these girls in a college program where they are running 7 days a week + doubling with consistent long runs and they will typically progress very well. A lot of high school coaches are much more conservative with their female athlete's training v.s. their male counterparts in my experience. It makes it all the more easier for a freshman to have a big impact immediately in a college program. Especially since the jump to 6k in college isn't that drastic.
I am obviously not your coach, but as an outsider looking in....it would seem that you need to maintain tempos and mileage for longer. Race intervals are cool (and necessary) for high performance, but also if you are racing frequently then, well, what more specific workout could you do than an actual 5k race? Hope this information helps.