Demanding Bride

I'm allowing my bridesmaids to choose their own gowns. They're coming from the same designer group (Dessy), same color, not sure about fabrics. I asked them to check out the website and choose a few dresses that you like and give me the list. All but one have done that-its eight all together. So, today, I decided to look at the dresses they chose and write down the descriptions, including the fabric. I ended up writing on a few of them that I don't like it, or hate it, or too old looking, or the fabric is not right. After I did that, I let the girls who had the least amount of selections left to go back and pick more young, fun looking dresses. My sister told me to let them just wear what they pick since they're spending their money. What do you guys think? My wedding is semi-formal but its in the evening. I don't want my girls wearing dresses thats too dressy or look like a 40 year old (no offense) is supposed to be wearing it.