If you go looking for Ariel in her grotto, arrive early! When we were there last September (the slow time of year) people were lining up 30 minutes before Ariel arrived. So one morning DH took DD on the fantasyland rides wil I waited on line. Most families did this. They joined me when the line started moving. It took us about 5 monutes after that to meet Ariel.
If I hadn't waited, it probably would have been a much longer wait for DD. The line goes in the grotto, so it would have been hard for them to get to me once it moved. This way, I did all the waitaing and DD joined at the last minute.
She was thrilled to meet Ariel. Little Mermaid was her favorite video at the time.
I don't think she appears at the breakfasts, since she is in Mermaid form and would not be able to walk.