What is the best teaching assistant qualification to aim for?

I do not know of any teaching assistants applying now who do not have a degree and lots of experience in schools.

IMHO TAs are exploited because they are paid peanuts and often expected to undertake tasks that should be done by a qualified teacher. Unfair to TAs and to teachers, not to mention the school children. I should encourage your daughter to train as a teacher if she wants to work in a school.

If she wants to work with young children she needs an EYFS recognised qualification Level 3. With this she can work in schools and nurseries. I am not sure there are any home-studied courses because it is a practical course. She can become a classroom TA without any formal training but she would probably need to have experience to get as far as interview.

I'd be careful about courses being offered. Some may be useless. Check with the General Teaching Council about what qualifications.

Has the school offered her a placement?

Thanks DaphneBroon, valid points which need taking into consideration.

I am afraid I don't but I would just beware. So many TA jobs have been axed and even qualified teachers who are looking for something less stressful are finding it hard to get a job. Obviously it varies depending on region. Pay rates are low, so nobody is in it for the money, but the satisfaction of making a real difference.
Best of luck to her!