It doesn't say that she gave them a brush Caylee had never used, does it? It just says she didn't give them the one Caylee EXCLUSIVELY used. So unless the brush handed over had never, ever been used by Caylee, I don't think we'll see obstruction or tampering charges.
What is more interesting is why LG would know about this at all. Did Cindy tell him? If she did, did she tell him because she didn't think she had done anything wrong? or did she confess to him that she tried to hide evidence? Context would be appreciated!