This doesn't sound like the normal Letsrun complaint from a runner who races their workouts and can't keep up in races but make sure your workouts are not races. I'm not sure how you are converting your workouts to race times. Is low 19 what another girl on your team who did those workouts with you ran?
Can you compare the weather on the day you ran the hilly 5 miler and for the race? How many races have you run this year? Sometimes you just need to run a few races to bust the rust from your ability to hang on.
While I'm an old guy and not a HS girl, I could do any of the training you list but would never run low 19s. For me, I can run 800s on the track, even a 2:45, especially with standing rest between them. I can also cruise along at 7:00 pace. My weakness is on a XC course, the grass and soft footing just take all my energy.
The first thing that makes the energy stealing footing worse is if I go out too fast. Going out slower really applies to the first 400-800 m. You can still run a pretty fast mile split as long as you don't try to run it as 90, 100, 105, 105 this is MUCH harder than running 100, 100, 100, 100. Much better to run the first 400 too slow like 110, 100, 100, 100 than too fast.
I have found that making sure I practice running on bad/soft footing helps, even just making sure to run on the grass next to the side walk for the first half of about half of your runs should do it.
The next question is what time of day was your 22:10? If you do all your training at 4:00 in the afternoon and then try to run an invitational at 9:30 am your body may not like it. Make sure you do some of your practices in the morning if your big races are going to be in the morning.