For everyone who's seen my earlier post about bridesmaids dresses, you know my search has had quite a bit of drama

I'm happy to report that I now have found a dress for my 4 bridesmaids (Alfred Angelo style #6493 - Satin - Eggplant). The question I am now faced with is what to do about my maid of honor's dress. She is awesome and told me she would go with the dress the bridesmaids have if that is what I wanted but I know she has kind of fallen for a different dress that makes her look amazing (Alfred Angelo style #7139 - Chiffon with Satin sash - Eggplant). Thinking it over, I kind of like the idea of her being in something a little different to stand out - especially if the satin sash on her dress matches the satin of the other girls' dresses, but I am a little bit concerned about the fact that her dress will be a different base material and that may be something you aren't supposed to do? I'd love to know if people think it would look okay or awful that the fabrics (and inevitably, the color since one is a shiny material and one is matte) won't necessarily match exactly. Links to the dresses are below. All thoughts are really appreciated!
http://www.alfredangelo.com/collections/styles/6493http://www.alfredangelo.com/collections/styles/7139