I have a bit of experience in this as in I have worked with a number of YP who have been homeschooled, for various reasons.
IMHO it works well if it is a conscious choice and carefully planned; it also can be expensive indeed, especially for exam years. It's one thing to teach your DC the basics of reading and maths and pursue their other interests when they are 6yo; it's quite something else to teach them GCSE-level work.
I am a teacher and MFL is my subject; I would feel confident in other subjects too (English for sure, history, maths maybe) but no way could I support a YP through GCSE physics, for example.
So firstly, what is your DD's take? Does she want to do this? Has every other option been explored?
Secondly, what is your plan? Online school (a friend uses this and it is very good but also very ££)? Do you work – will you give up your job or can you or someone else be there to offer support? Could you use tutors?
A lot of HE YP IME take GCSEs (sorry so many acronyms!) a few at a time over some years, but often starting in year 9; this is obvs not an option but still it may be an idea to stagger the GCSE exams over a couple of years. She can start her post-16 education aged 17 as you have three years of funding.
And yes, look at where she could sit exams. Would school be willing to be an exam centre for her (possible, perhaps)? If not then there are exam centres across the country but yes, depending on where you are you may have to drive and the exams are not cheap.
If you do do this I suggest strongly you prioritise maths, English lang, English lit maybe and combined science (IGCSE may be the way here as there are no practicals I think) to give her a decent basis going forward. All the best to her.