I'm not a fan of underwires, especially for teens. Their breasts haven't even finished growing yet and we need to corral them with metal antennas that could restrict the lymphatic flow? Yikes. Just doesn't make sense to me. But all the cute bras are constructed that way. And we all know how important it is to have a cute bra!
Enter my friend the seamstress with a magical solution. It's called a seam ripper, and is available pretty much anywhere ... Target, the grocery store, or of course, a fabric store. You can see a picture and read about it here: http://en.wikipedia.org/wiki/Seam_ripper
You can buy whatever fabric and style your daughter wants, and when you get home, turn the bra inside out and use the seam ripper to cut a tiny slit in one end of the sleeve that holds the underwire. Push the other end to pop the little white tip out of the opening, and the whole underwire just slides right out.
You can just leave the slit there, rather than sewing it closed. It won't unravel in the wash or anything. The modification is completely invisible.