My 3-year-old daughter can count well (I guess that is relative, but anyway). She understands the idea that numbers represent quantities. If I ask her how many pebbles she has or how many steps there are, etc., she will count out loud and give the right answer. She counts beyond 10, but it gets more fuzzy over 10. She can even do some basic arithmetic. She also gets the symbols right for each number most of the time.
The problem is that she always skips 7. She goes straight from 6 to 8. I correct her and then she gets it right, but the next time she will skip 7 again. She has been doing that for as long as she could count which is since she was about 2.
What should I do to change it?