I agree with both the above comments... You have to remember she is only 16 and still very immature. I feel that since you already offered her the 'junior bridesmaid' position, that, that should be sufficient. You did your part to make nice, now you do what you want, which is not have her in it. If she really wants a dress you can make her an "honorary bridesmaid" and pick out a dress that matches your colors, so it still looks like she is apart of it, but really she'll have nothing to do with it! I personally think that you need to concentrate on you and your FI and do what makes you happy. It puts your FI in a tough spot, but it's not always up to you make things peaceful. I hope this blows over for you very soon!!!!!!