If you are concerned about being advanced causing boredom, I think it might be too late to prevent her from becoming bored in class in math, so I don't think I would prioritize this as a reason to hold her math development back.
Though clearly, if she is happy at school, she is still getting something from the experience, even if it isn't math.
With children at a comparable stage, I have used SM books, basing placement on performance on the SM placement tests. (If you encounter terminology that she hasn't seen before, that is easily remedied by teaching her the SM terms, and moving on with the concepts.) I think little ones still prefer hands-on to online. But that would depend on your child. As to US Standards vs CC, I've used Standards, and liked it, but I don't think using CC would be terrible, either. I will note that the problem sets and review questions in Standards (and the older US edition) are very carefully designed to continue reinforcing and reviewing topics from much earlier, even when they are not among the ostensible review topics for that set, so there is something to be said for maintaining the sequence established in the Standards edition.
Another thought, for a young child: unless your DC particularly loves workbooks (and I've had those who did, and those who didn't), I would suggest purchasing only the textbooks, and working most problems orally, or on separate paper. There are plenty of practice problems in the textbook, so you don't really need both. The textbook is in color, which young children often enjoy, and includes the explanations of SM instruction, which the workbooks do not. If you happen to have learned most of your elementary math in a SM-similar way, you might be able to figure out the methods just from the way the workbook problems are laid out. If you haven't, then the textbooks will be very helpful.
