Going crazy here as I have replied now THREE times and for some reason it keeps getting lost and messed up. Hope this still makes sense as I am sick of retyping it!
Breakfast cereals tend to be fortified no matter who they are marketed to - so your Corn Flakes are just as fortified as her baby cereal. If she won't eat baby cereal any longer then you can offer her any other breakfast cereal that you are willing to let her eat. Even your highly sugared turn-the-milk-blue cereals are probably almost as high in iron!
While breakfast cereals are an important part of a diet as a carb/grain option, they aren't crucial to iron intake. In fact, if you are relying on them for iron, she may not be getting as much iron as you think!
There are two types of iron:
Heme iron, which is easily absorbed by the body, is found in foods such as red meat, poultry, liver, and oily fish. When we consume these products and make efficient use of the iron -- 15-35 % of the heme iron in them is absorbed by the body. This amount is not significantly affected by other dietary factors.
Non-heme iron is found in foods such as fortified breakfast cereals, pulses, nuts, soybeans, molasses, raisins, and spinach (among others). Non-heme iron is not used very efficiently by the body -- only about 2% - 20% of the iron is actually absorbed. The iron absorption is significantly affected by diet. Firstly, the body needs vitamin C in order to help the non-heme iron to be absorbed - no vitamin C in the diet and the iron absorption rate will be much much lower than the amount being consumed. There are also foods which decrease the absorption of the non-heme iron - tannins in tea, calcium, and phytates (substance found in legumes and whole grains). So a cup of milk on a bowl of iron fortified cereal would be better replaced with a glass of orange juice!
Not sure if that helps or not - I would still encourage her to eat cereal if you can, but not be concerned that it is baby cereal. And, make sure that if her main source of iron is from fortified cereals or other non-heme sources, that it is getting absorbed. Getting some good heme iron in her diet will help as well!
HTH!