I understand where you're coming from, even if other members do not.
I'm assuming that by "falling back on law" you mean ANY law course, you all have to remind yourselves that there are various law degrees you can do an no you do not need 4 A*'s and to have no social life. I know many people who simply did college courses and are on business law courses so the world is not so morbid for your daughter.
Additionally, and I'll be encouraging, at least she's giving it a shot and a second chance, and assuming she's had the worst shock of her life she'll give it all she's got this time around. You've said she isn't going to college, which is obviously a good move. We must all remember that in order to get on AS courses they look at your GCSE Grades not anything else, which clearly your daughter did well in.
Although doing both sciences isn't the best idea, at least doing one and getting the minimum entry requirements for the course at least is a good idea, whether you do this via a home study course or not. Just ensure your daughter puts the work in and I don't see why you shouldn't believe in her.
Additionally I think Nickschic you're being out of order almost insulting Kismet and her daughter, who clearly has some ability. I know as well as anyone, being a sixth form student, that at times like these we need encouragement not whatever you're offering.
Your daughter should look at the partners scheme also, as this can help with entry requirements and gave me a load of hope when I was feeling down about my A-levels.