It's likely today has been a catalyst for her mental health crisis.
I can relate to that. I failed all but one of my GCSEs, and was made to feel a total let down to my school and family. It was the first year of GCSEs so there was a lot of media around, much more so than subsequent years, and I was pushed off to the side for failing.
I managed to get to uni and have had a successful career, though I cannot work anymore due to health issues. I struggled a lot going into my third year around GCSE results time, I have depression, anxiety and PTSD (no help possible) - it shouldn't but it's still an upsetting day for me. I really wish there was more done to help GCSE and a-level pupils prepare for whatever results they get and help them find a way forward for them in what they want to do. Instead of what I got which was a sarcastic comment about being thick and directions to my local supermarket as I couldn't expect more and I wasn't allowed to talk to the careers advisor.
I did more, but it left its scar (as well as others I won't go into here). Your DD can totally achieve whatever she wants, honestly. I have one GCSE yet I have been a researcher for a uni, a lecturer, I've represented my university at a world conference and taught and managed a NHS department. I have a undergrad, postgrad and professional degree.
I had two interviews where I was asked why I failed my GCSEs and didn't do a-levels. The first I fought for the job and it was horrendous. The second time they refused to discuss anything but my GCSE choices so I got up and left.
I have other things on my cv like playing an instrument but I never followed any guides when doing a cv, none of the stock phrases and the jobcentre have always hated it but employers generally have been happy with it.
When my school asked for people to talk to those doing their exams this year they wouldn't let me do it because they didn't want a failure talking to the students - despite everything I achieved afterwards those results are still what counts to them. It can be very very difficult to see beyond such things, depression can and does mean you latch on to things others might not.