jmc

Let $\text{Day }1$ to $\text{Day }2$ denote a day where one coupon is redeemed and the day when the second coupon is redeemed. If she starts on a $\text{Monday}$, she redeems her next coupon on $\text{Thursday}$. $\text{Thursday}$ to $\text{Sunday}$. Thus, $\text{(A)}\text{Monday}$ is incorrect. If she starts on a $\text{Tuesday}$, she redeems her next coupon on $\text{Friday}$. $\text{Friday}$ to $\text{Monday}$. $\text{Monday}$ to $\text{Thursday}$. $\text{Thursday}$ to $\text{Sunday}$. Thus $\text{(B)}\text{Tuesday}$ is incorrect. If she starts on a $\text{Wednesday}$, she redeems her next coupon on $\text{Saturday}$. $\text{Saturday}$ to $\text{Tuesday}$. $\text{Tuesday}$ to $\text{Friday}$. $\text{Friday}$ to $\text{Monday}$. $\text{Monday}$ to $\text{Thursday}$. And on $\text{Thursday}$, she redeems her last coupon. No Sunday occured; thus, $\boxed{\text{(C)}\text{Wednesday}}$ is correct. Checking for the other options, If she starts on a $\text{Thursday}$, she redeems her next coupon on $\text{Sunday}$. Thus, $\text{(D)}\text{Thursday}$ is incorrect. If she starts on a $\text{Friday}$, she redeems her next coupon on $\text{Monday}$. $\text{Monday}$ to $\text{Thursday}$. $\text{Thursday}$ to $\text{Sunday}$. Checking for the other options gave us negative results; thus, the answer is $\boxed{\text{Wednesday}}$.