You could try making some little cards that have numbers on them (the actual digits) and then the correct number of circles to match that number and have her put objects on each circle. Then she could actually physically see what is bigger and smaller.

You could also just make cards that have the right number of stickers for the digit shown. The visual on a larger vs. smaller group might help her.

Practising finding before and after numbers can help too-- so if you were to ask her what the before number for 4 is, she would say 3, and the after number would be 5.

I'll keep thinking on it, but those are my ideas off the top of my head.