In the Harry Potter series, was Nagini a horcrux?

I know that there were supposed to be 6 horcruxes and then voldemort himself. the book also says that voldemort was going to make his last horcrux after he killed harry, but as we know that didnt work out so well. so did he ever get the chance to make nagini a horcrux? there was already the book, locket, ring, cup, and the diadem. anyway if you have an answer id appreciate it.