Let be "x" the percent of her monthly income spent on food.
You know that her total income per month is $2,500 . Then, you can identify that this is the 100% of her monthly income.
According to the information given in the exercise, she budgets $375 per month for food.
Then, knowing the above, you can set up the following proportion:

Now you need to solve for the variable "x". This is:

The answer is: 15%