You don't mention the Art of Problem Solving one, which would seem like one obvious choice; looks as though one instantiation of it started yesterday, but she might be able to join in! I have no experience of their courses (the timing doesn't work from Europe) but I love their books and Alcumus.
At the other end of the spectrum, my DS just did ALEKS Algebra 2. Depending on what "rigorous" means to you, this might not be suitable - all students have to do is enter answers, so it's no good for practising writing proofs etc., and the questions all fit into neat boxes, so there's no open-ended problem-solving element. I felt it was useful as a way to give DS a largish toolbox of techniques, though, and that this combined with using Alcumus and other problem-solving materials was good for him.
