Okay, I'm going to sound like a broken record.
The bend you had around the barrel at 3:13 --> do that EVERY
time. Most of the time, you are missing that "over-exaggerated" bend that you used to have with her, and you are going into the turn too straight.
She still swinging her butt. Go deeper into the turn to make her engage it. Once such instance is at 0:36 which you did correct her for on turning it a second time. Another instance was at 3:31 where she swung and you went to circle it a second time, and then at 3:39 you let her swing AGAIN on your second turn around the barrel. Do not let her leave that barrel until she uses her butt and doesn't swing it; even if you have to circle it 15 times. 5:32 was another bad butt-swinging. This has become a bad habit for her at this point, and it's going to take great consistency on your part to fix it.
Here's what I mean about pushing her deeper into the turn. In this freeze-frame, you started the turn too early and she kinda "cut" it on you. In my mind, it's waaaay easier to tighten up a turn when you've been purposefully sending them deep in the turn ..... than to try to fix a horse who turns too early, cuts the turn off, and knocks a barrel.
Some turns you gave her enough room; some not. That takes better consistency from your part. Strive to ALWAYS set her up for that perfect pocket.
Getting more bend in her body will help with the swinging butt problem too, especially if you bend, bend, bend so that she relaxes and drops that head.
You do a good job of making sure she keeps her hip IN before the turn.
At 6:20 when you asked her for a lope, she actually stayed on her butt wonderfully. The turn itself wasn't great
but she stayed on her butt!!!! That is another instance where you should push her DEEPER before turning; especially when you are loping. And remember to keep the BEND. Your forgetting that at the lope, probably because you're trying to keep her slow. Watch at 7:14. You went in completely straight to the turn, until the backside. She should be bent and ready as you come into your pocket.
I think some counter arcs before the barrel turn (and then don't turn it) would help Squiggy's worrisome personality. Or purposefully making all your barrel turns huge, and focus on bend and engaging the hindquarters. I think she's getting nervous to the fact that you send her in straight, and then expect her to turn it super tight.
Out of all the loping turns, I think your best one was at 7:54. Notice how you went into the turn with room in your pocket. She had a little bend in her body, but she could have more. But I'd still give her more room at this point. If you take it THAT tight at slow speeds, guess what happens when you add real speed? That turn is going to tighten and she's not going to have enough room.
1) Bigger pockets at slower speeds
2) Engage hind end
3) Bend, bend, bend!
4) Go deep into the pocket before turning. Maybe a goal you could set for yourself is do NOT turn until Squiggy's hip in at or past the barrel. At this point in training, I don't mind if a horse goes past the barrel a little bit, because once you ask for more speed, that'll tighten up on its own.
And..... I still love your dog! So cute how he/she follows you and Squiggy around!