The skirt sounds lovely and I agree with the others to let it be the star. If you have some jewellery a very plain top could be just perfect. I would probably stick to a black top and wear "bling" to liven it up as I think a black column can be more flattering to an apple shape.
With the "meeting your idol" I am sure she will be more interested in what you have in common than what you are wearing. It sounds like you are covered here in your own wardrobe.
For both occasions I think a lovely hairstyle, a small amount of makeup and a lovely smile is the most important thing.