You could also try getting Aurelia's money in her chest above the diner or try for both. The achievement has unlocked for me, though I'm not sure with which money it was triggered.

I did Malleolus' money in Claudia's room. Shot her, stole the money, and it counted for me.

I believe that the money in the chest behind the blocked door isn't considered stolen money.

As Secondhook mentions above me, stealing Malleolus' money is your best option.