"You have 7 months to prepare her for school.
Either that or homeschool yourself but accept that it may then be permanent."
That is ridiculous. It is not a case of now-or-never when it comes to starting school. It really is not. Home education isn't a life sentence.
I am astonished by predictions that keeping a child out of school - or even part-time - for a term or a year will prevent her from ever becoming independent. I have known dozens and dozens of home educated kids who started school later than the usual age in this country. It is not a problem. Children mature. You don't have to DO anything to them to force that to happen.
The prospect of leaving mum may be daunting at four, but feels natural to them as they get older. It starts with visiting grandparents, and then they go into the neighbour's garden for a bit. They have a playdate with a close friend where they already know the other parents well, and then have playdates with other friends where they DON'T know the parents well. Maybe they move on to Brownies, or feel able to stay at dance class without parents. Then they end up on a week-long half-term drama class. They go into the corner shop while mum waits outside, then they go up the road to the corner shop alone, then they go further to a friend's house or the library by themselves.
Not all children are on the same timetable. But they all grow up.
There is something to be said for starting school later than four. All those little things which can feel overwhelming to small children at school are easier for big children to take in their stride. They can go quite happily for six hours without a cuddle or a nap. They can easily manage the toilet alone, sort their own clothes out, and have no fear of the hand dryer or the bigger children or the loud-voiced lunchroom assistant. They have the sense to eat their lunch because they realise they'll be hungry and crabby later if they don't. They have the confidence to ask for help when they need it rather than suffering in silence. They can go most of a day without someone who loves them by their side. I do know that some four year olds can do all of those things effortlessly. Some can't. The proportion of seven-year-olds who are still unable to do those things is much smaller. The simple solution to achieving school readiness is to wait.
OP, what if you aim for your daughter to start school in January and defer her entry until then? When the time comes, if she doesn't seem ready then instead of deciding that you should have sent her in September, you could decide that you ought to wait longer. The older she is, the easier it becomes to start school. Home education is straightforward and doesn't have to involve anything you wouldn't already be doing with her: reading to her, talking to her, playing games. You're educating your child already. In that sense, keeping her home past the start of compulsory school age is just a technicality. (The only serious disadvantage I see to this is that if she has a place at an oversubscribed school, she'll lose it if she doesn't start by January.)