How can I get my 2 year old off of her pacifier?

Initially it was just something she want to help her go to sleep, but now its becoming an all day thing. When she is around others (neighbors, company, outside, etc) she does not want them to see her using it, so she is aware that it is not acceptable. In the house, she panics if she doesn't find or if it is withheld from her. what to do??????????