Math is the study of numbers. All that is required to do math is to be able to count to 9. 
Many skills can be learned using the Numeral ID kit:
number identification, color recognition, the ability to count to 9, sequencing, fine motor skills
Each Numeral ID Kit contains a plastic tray, colour number cards, and one each of the 1-9 blocks.
Play around with the virtual blocks and cards on the whiteboard below. You can toggle the board to full screen, zoom in and out, pan around, move and rotate the blocks and cards, and undo and redo actions.
I ordered this during the Christmas sale for a new client. She has Down’s Syndrome, spent six years in elementary school, and doesn’t have the one-to-one correspondence yet.
That’s so sad but this should definitely help. It will take patience, practice, and time though. There are a lot of other games and activities that you can play with her that will help build those skills as well.