You have to cut her solids back (just as everyone else as said) A baby that age should be drinking 28-32 oz of milk (breast or formula) if she isnt then there are too many solids. Of course the formula you use in the cereal counts too. You might want to try bottle only for breakfast and lunch and a nice two oz porridge (grain) for dinner. That will stick to her tummy and keep her sleeping at night. Then gradually introduce 1-2 oz additional food as her milk consumption increases. :) Everybaby is different so the amount someone else is drinking isnt a perfect guideline, growth of your child is the number one indicator, but do be aware that solids do directly affect milk consumption and please know I am not even close to anti solids as my little one started them at four months and is a healthy 19 pound 7 month old - every one is different!
Another thought you may want to make her grains (and other food) yourself if she is cutting back on milk she will need all the nutrients she can get from her food - its really easy and quick you could PM me if you had any questions :)