Whats the relevance of the topic? It seems completely off topic when your question is not about two copies of the wallet.dat.
After trying to send bitcoins gor error:
The transaction was rejected! This might happen if some of the coins in your wallet were already spent, such as if you used a copy of wallet.dat and coins were spent in the copy but not marked as spent here.
How to fix this?
launching bitcoin core with
-rescan should fix this. Did you try that?