I have to agree with Brit, Beneful is a horrible food. You've gotten some good suggestions here on how to work around it with your mom, i'm hoping it works. If you don't feel comfortable feeding this food then it would be best to switch, as her owner you should feel confident and have peace of mind in what she's eating.
Does your mom mind in switching her dogs food? is she willing to try others? maybe you can show her that this food is not so good by breaking down the ingredients to her. Show her that there are healthier options that you're willing to pay for and maybe she will come around.
Here is a vet who is discussing bad dog foods, at the 8:17 mark she picks up a bag of Beneful
The Quality of Pet Food Ingredients (Part 2 of 2) - YouTube