You could have a talk. Maybe discuss with her the location she keeps her "food". You obviously can't tell another adult what to eat, but you can make your needs clear. I am lucky that my wife always ate "healthy". You know, vegetables and fruits. But if she buys some chocolates, she keeps it in her office.
When people fail within two weeks it's because of discipline and motivation. Motivation never stays around longer than that, and discipline soon makes its exit known as well.
Instead add focus (make a list of rules, on paper). Create a system, routine. Make a blueprint. Track your progress, as in write down successful days, write down unsuccessful days. In days you'll find you can look back to something akin to a "bank statement" with regards to your eating habits.