My daughter is 11, she has been wearing those tankini tops underneath clothes for a few months. They have a built in crop which gives the fabric a few layers. She has some cotton crop tops as well, but she is not ready for them (her words). She doesn't like that you can see the crop top, she likes the tankini as it goes all the way down not drawing attention to it. Big W have a great section in the bonds wear with all sorts of options I would take her there and talk about it together. I didn't want to bring too much awareness to it all before she was ready, so I just said things like, let's just buy them and put them in the cupboard for when you are 'ready' it was great for opening up the conversation, as she was not even aware that I could see through her shirts or dresses so I didn't want to make her too self conscious.