Ok this is what my pedi told me with my son. All babies are born with enough iron in them to last 6 months. That's why they usually recommend rice cereal enriched with iron because you don't get iron from breastmilk starting at 6 months of age. Some people start solids at 4 months but it's not necessary until 6 months of age. If you are using formula, that's a different story. Rice cereal is recommended to use first because rice has the lowest allergy issues with most babies. But usually you can start adding different kinds like oatmeal as they get older so trying different type of cereal is good. Also, if you are breastfeeding, it's good to mix your milk with the cereal so they are eating something more familiar. My BG is not using bottle at all but when I can I try to pump and freeze for when she starts her solids.
Other moms had some good advice too. You can talk to your pedi about iron supplements and ask how much she should be getting or find other foods rich in iron that your girl might like. Every child is different so you'll have to try different things for your girl. Oh, my son usually had his food warm where as I know lot of other babies didn't mind the cold food. You can try warming up the food to see if she prefers it or colder.
I don't think I gave my son that much cereal when he was 7 months old. I think I fed him 3oz of cereal around then with other fruits and veggies. I always gave him new food in the morning and then give him rice/oatmeal cereal in the evening. That way if the new food bothers them, it won't keep him up all night.
Good luck and hope some of these advices work for you!