Replacement straps exist, but you are all trying to put them in the wrong place. The technique is to add the replacement straps to the bra, not the dress. Then you wear the strapless dress over the bra and let the decorative straps show. You also (of course) could sew some hook & eye fasteners to both the bra and the dress to stop any downward movement of the dress. (Though, honestly, if your daughter is in the sort of environment where kids do that on a regular basis, then she needs to find a new set of friends.)
http://www.brastraps.com/index.htm
And yes, they do have rhinestone, though it is a lot cheaper to just go to a fabric store and buy a new strip of rhinestone beading to replace the strap that broke. Just stitch it on by hand.
If you want to use straps like these on a dress itself, then the technique is to securely sew a 1/2" ribbon loop to the inside of the dress where the strap can clip onto it.