Who is the girl that host of Disney commercials at World parks?

It's impossible to say definitively who you're referring to without more information. Disney has used many different actors and actresses in their park commercials over the years.

Could you provide any more details? For example:

* What year did you see the commercial?

* What park was the commercial for?

* Can you remember anything about the commercial itself?

With more information, I might be able to help you identify the actress you're looking for.