Park it in her pen and feed every meal in there. She'll get hungry enough to go in on her own eventually.

Then re-teach "forward" on the ground over logs, over tarps, over bridges, a large step up from a low ground up onto high ground (like you see on trail challenges, can't find a pic right now), into dark, tight spaces, etc. To me it kind of sounds like she has your number, so try everything the next 938465436 people tell you try and persevere. Work on it every day.

If there was a vet student action figure, no children would buy it, and it would need to come with a warning label about increasing the depression in teenagers. Even the commercials for it would be depressing:
The new vet student action figure from Mattel! It has foldable legs for long periods of sitting and standing! You can watch its hair turn gray before your eyes! Comes complete with 50lb backpack and scoliosis! Happiness not included.

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