What am I?

The fairy mixed with angel,
A mermaid yet a witch-
What am I
Besides what I am within?

When I walk inside a forest,
I feel the plants in my fingertips,
I make them grow faster
As a flower unfolds in my hand.

When someone's crying,
And they tell me their woes,
Whatever they do,they think I don't know...
But their luck changes the next day.

When I'm swimming the water calls out to me,I jump in with my serenity- And I never get out.

When I need to curse someone,
Or make a charm...
Lets just say it works ;)

So....
What am I?