Are you both on the v3.1.1 wallet?
These outgoings sound like they're the Development Fund fee - it was outlined in the changelog document when it was released. It's to help the team fund the projects that are being worked on.
It's advised to backup your wallet.dat file after each time the fee comes out, as it generates a change address - don't just dump the private key, copy the file itself. You can either do that or send all coins back to your main address. Or do both, of course!
Why do we have to keep backing up our wallet.dat each time the wallet decides it wants some of our coins? What is the worse case scenario?