My DD was in this position and it had never entered our heads she wouldn't get the required grades, so it was a complete shock and panic.
The 6th form offered her subjects that were not suitable at all and would not have enabled her to continue on her chosen career path. Eg dance and photography.
We had a mad scramble for a few days, an interview at college and she got a place on a level 3 btec course that would be accepted for her chosen career course.
She has just finished her 3rd year at uni, and despite my panic and dds tears at the time, I look back and think it was the best thing for her. Continuous assessment is much better than end of 2yr exams imo. It better represented her abilities and gave her better study and essay writing skills than she had, setting her up well for uni. Being treated like a young adult, a different set of peers, and actually learning about what interested her instead of generic subjects. And she learned that if things don't go as hoped, all is not lost.
I didn't go to school in the UK and had the impression that colleges were somehow 2nd best, or for the less academic but I'd argue this now.
My 2nd DC has just completed college, and is hopefully off to uni in sept, and dc3 is planning on going to college in Sept even if she gets grades for the 6th forms she has applied to.
My advice would be to spend the time researching local options, that will be accepted in her chosen area of uni study (if this is her hope). Colleges (in this area anyway) are usually good at taking late applicants after results day, so don't worry about applying now but it would be good to have a plan b if results day doesn't go as hoped, so you can act quickly if needed.
And remind your DC, our grades don't define us, only open or close doors, that perhaps we are/are not meant to walk through.
All that said, I hope results day works out well for your DC.