This one is called Hiprose …

One of the tricks the river girl used was to make herself invisible and proved to be invaluable as life (or the moods) went on.  Some days she would like to be noticed and others she didn’t.  The trouble was that she didn’t always know which way her mood (as her mother called it) would take her.  The mood was as unpredictable as the tide. The mood and the tide were one of the same she had to be ready for both.

In a ‘real’ fairy story, a fairy might make a spell with a rosehip to make herself invisible, for the girl they contained itchy powder no magic potion.  So, she would steel herself, to run like fury in the opposite direction or sidestep into a holloway and take another path.  Or smile and ask him or her to see her across the road.