Mini Freak Out On Bridesmaid

I am having such an odd wedding non-wedding but it is the wedding I want. We are getting married in a National Park so while the area that we are having the ceremony has a few benches, it is essentially standing only. The few benches in the space will be enough for some of our elderly/disabled attendees. That being said, I kind of told my Bridesmaids that I don't really know how it is going to be, like they might not be standing up with me or maybe they will but because everyone is standing, I don't really know how it is going to go. But I made clear that either way, I still want photos with them as my Bridesmaids. I also told them that I don't really care what type of dress they wear, long or short. I only asked that they wear grey converse with a black dress that isn't too busty. Everyone already has the converse because it was a seasonal color so we got those last year. So since I don't care the style of dress most of the girls haven't gotten theirs yet. I mean, you can buy a black dress at any department store or even amazon. I have made it clear I don't care. Just buy a black dress that you like so you aren't wasting money.
So now to my issue / mini-freak out.
My Sister is terrible at shopping so she spent the entire weekend trying on 1000+ dresses and finding nothing. So today I am trying to get some ideas and help her out. One of my Bridesmaids sends me her list dresses she found that she is looking at so I can send to my Sister to help her. I so appreciate this, of course! But several of the dresses on her list are VERY busty and a couple don't even come in solid black. Then at the bottom of her email she says "Most come in different colors, so we could do black, navy, gray, teal... mix and match, etc." Are you serious?
I said something about this to one of my other Bridesmaids and she said, if she picks one that is too busty to just be honest and then she says, we know all black. I am not confident that we know all black if she is looking at dresses that aren't all black and making those suggestions to my sister. So... Do I respond to her email and say thank you and then just re-iterate all black or do I give her the benefit of the doubt and wait for her to start making decisions?