Op I am not sure why you think it all seems to hinge on the predicted grades from the college and I am sad for her as her aspiration has always been to be a vet and now she seems to have lost her way
Yes, an offer this year will hinge on her predicted grades, and is unlikely if the Chemistry prediction is only a C, but if being a vet is her aspiration then surely her No 1 goal is to ensure she gets AAA at A level next year, with whatever re-takes are necessary, and then she can take a gap year and re-apply.
We have a similar situation with our son, who got a D in AS chemistry, which he wants to study at Uni, but slightly different in that there are extenuating circumstances. He had serious medical complications in May half term and was in and out of hospital for a week, resulting in him getting a U in Chem 2 exam, taken day after final hospital admission, compared to a B in Chem 1.
He has been told by head of 6th form that he should still apply this year, as she will include details in UCAS reference and he is still being predicted an overall A (with a resit of Chem 2 obviously). However, we have discussed with him that he may need to have a gap year and re-apply with results, if no offer is forthcoming this year. He knows that what matters most is that he gets the required grades next year, whether he has an offer or not.
At one point in the hospital saga we didn't know if he would even take his last 3 exams after half term, and re-taking Year 12 was a distinct possibility, so if he ends up deferring Uni for a year, it will be a minor inconvenience.
A local girl we know was hoping to start Vet school last year. She dropped 1 grade, getting AAB, but re-took the relevant subject, and has just gone off to RVC. Her offer last year was for a different vet school, so having to re-sit & re-apply did her a massive favour in that she actually got into her No 1 choice!