Since she's 6 months old, she could be needing something more substantial before dinner, as you're thinking. However, I think I've read in multiple sources that putting cereal in a bottle is NOT recommended (but can't remember why).
You should try to feed her some cereal before bedtime from a bowl/spoon, since she's 6 months old. I always started with a breast or bottle feeding, so that I knew my baby boy was first getting all of the nutrients from milk or formula and then would follow up with solids (at 5 months of age we started him on some rice cereal and then later added vegetable baby food and/or different cereals like oatmeal, which has more fiber and would keep him full longer). At about 6 months, we also started giving him Cheerios (which he still loves at 22 mos), once his pincer grasp was evident (and after he'd already been eating rice cereal, and other solids for awhile).
Something you may also want to consider is that there's something else wrong. If she's always been a good sleeper and suddenly something has changed...it is probably not hunger (although she'll happily take a feeding from you when she's upset, because it is comforting to her).
I can only speak from my own experience, but for my baby, teething was an issue at that age. Is your daughter doing a lot more drooling than normal and seems to be chewing on everything, like her fingers?
I found that giving Connor a little Motrin Infant Drops when he was cranky and teething, holding/rocking him for only a minute, and then patting his back to get him back to sleep, really did the trick (we found that Motrin works much better than Tylenol for pain, while Tylenol is a better fever reducer). We only had to do that for a few nights to get him through the worst of it (until the next time, of course), which is good b/c I try to use the Motrin/Tylenol veeeeery rarely. And, I think rubbing him on his back and not actually holding/rocking him back to sleep helped him to be at least partly self-soothing.
I'm just not sure that I could do the crying out method. Of course, Connor was always a good sleeper and seemed to only go through periods of pain and unrest, so I wouldn't have felt right.
Only you can know what's best in your baby girl's situation.
I hope this helps!
Best of luck to you!