To be honest, I would continue to offer other foods as well as the bread. If she refuses the other foods, then she has at least had some calories from the bread and the formula. Many children go on what are called Food Jags. That is, they prefer one thing over everything else. A friend of mine had a child who would only eat hot dogs, cheese and crackers for a long time. If you continue to offer the other foods, then she has the option to eat other things.
You could also try putting other toppings on the bread. Peanut butter will give her some protein, hummas, jam, honey, mashed/pureed vegetables, grilled/broiled cheese, fish are all some things I put on bread for my kids.