Counting

Gisèle has unique way of counting. She knows how to count 1-10, and does very well if you count along with her. If you ask her to count by herself (or if she breaks into counting without prompting, which happens often), this is what you get:

1, 2, 3, 4, 6, 8, 9, 10, 8, 9, 10, 8, 9, 10, 8, 9, 10, 8, 9, 10... until something else catches her interest.

I wonder what 5 and 7 have done to deserve banishment in her mind?