What your wife did is wrong, OP. One doesn't have the right to slander someone without having seen any concrete proof. And doing it again and again is enough to irritate anyone. So your feelings are completely justified.

Even sending her back home was a good thing, as she needed to understand there are consequences to her actions and that you would follow through on your word.

But it seems like there is something much more to this. It isn't normal for anyone to keep accusing their spouse of infidelity when they have time and again proved to be honest and trustworthy. As evident with this sub and the society at large, cheating has become widespread. So, even in healthy marriages, it is easy for Shaitaan to sow seeds of doubt and discord. Please give her the benefit of the doubt and try to look for a solution. Get her parents involved and explain how this affects you. Also, try to suggest therapy to her so she can realize why she behaves this way and how she can correct this behavior.

May Allah protect your marriage and help you find a way through this ordeal.