Reading came easily, math concepts came easily. Rote learning does not. I'll think some more about visual representations I think. I feel like she does better with abstract discussion than concrete materials. Like she needs to be told (probably with a visualization) how to think about these problems, not to spend endless time manipulating beads or some such.
Then I would try the play with numbers approach and pattern concepts. You might like some of the ideas here:
http://www.gifteddevelopment.com/Articles/instruction/i90.pdfMy DS just told me today that he realized adding even numbers always gets even numbers, adding odd numbers also get an even number, but adding an even and an odd yields an odd.
He also likes the idea that adding the digits of a number with nine as a factor ends up with nine. And that you can move up the squares by adding the next odd number to the previous square:
1 + 3 = 4
4 + 5 = 9
9 + 7 = 16
I can't even imagine memorizing any addition past 10 when a process works fine.