To determine how many times Abby should fill her measuring cup, we need to first convert the total amount of flour she needs (3 cups) into the number of fills based on the size of her measuring cup.
Let's assume her measuring cup holds \( \frac{1}{4} \) cup (the common size for measuring cups). To find out how many times Abby needs to fill this cup to get 3 cups, we can use the following formula:
\[ \text{Number of fills} = \frac{\text{Total cups needed}}{\text{Size of measuring cup}} \]
Substituting the values:
\[ \text{Number of fills} = \frac{3}{\frac{1}{4}} = 3 \times 4 = 12 \]
Thus, Abby needs to fill her measuring cup 12 times to get 3 cups of flour.
The correct answer is A: 12.