You don't necessarily have to think of it as "dropping down a year" or not. Home education is far more flexible than school, and it doesn't always make sense to think of kids as being in a particular school year. Focus instead on what would actually suit your daughter rather than mapping her onto the school system. If you start off by thinking creatively about what the ideal setup would be for her, you may be able to look for the opportunities and create the environment which is best for her, or at least get a closer approximation.
She doesn't have to sit a big set of GCSEs all at the same time one spring. She doesn't have to do any at all. She can spread them out - home ed kids typically do a few at a time, and may do just the minimum number required to get into employment or the next level of education. For example, colleges often require five or six. Or she could delay some or all of them and do them at college after she is 16 (possibly alongside another course), though colleges won't offer the wide range of subjects available at school or at home. It may be possible to do some in an autumn or winter sitting, but check carefully because sometimes these aren't available to everybody and may be just for resits.
Unless your daughter has her foot on the accelerator because she is desperate to be on a certain college course in two years' time, I would slow right down and let her recover from her anxiety. There's no point going from the frying pan into the fire by rushing and stressing her out. If she's going at her own pace rather than joining in a class, there's no risk of being left behind.
Home educated kids follow all sorts of paths, some quite roundabout. The main thing is to be having their needs met right now. If their mental health needs are addressed and they are happy, the rest will fall into place. The worst that might happen is that plans are delayed by a year or two, which is no disaster in the big scheme of things.
As an example, my eldest had no immediate intention of doing any GCSEs at all. They knew they could always go back for them later if it turned out to be necessary - in particular, English and maths are often desirable. They planned to go straight into work. Meanwhile, they learned independently, doing art, music and sports coaching. Then they changed their mind and started a part-time Level 3 online art course in parallel with English IGCSE at 19. Unfortunately the art course was rubbish and they dropped it halfway through to resume independent art study, and also did maths GCSE via an adult college course aged 20.
Despite having few formal qualifications, they thought they might get a place on a uni foundation year as a stepping stone to a degree course, but were encouraged to apply for the degree course instead and had some good offers. The offers were based on portfolio, recommendations, and personal statement. They're now in second year at uni, getting brilliant results and absolutely loving it.
Until the year they applied to uni, they weren't at all sure what they wanted to do. Not everybody has an answer at the age of 14 to "what do you want to be when you grow up?" and even if they do, it may change. In such a situation, many people urge teens to adopt the "just in case" approach, as schools do, and pack in as many qualifications as possible as fast as possible in a range of subjects. But another approach is the "just in time" approach, in which kids adapt their plan as they go along. It can take time to figure out what they want to do and identify ways to get there. Meanwhile, they learn about whatever most interests them at the time. Motivation remains high and stress low when they are following their own lights. My kid found that approach worked really well for them.