DO NOT PUT CEREAL IN THE BOTTLE.
if you want to try starting solids, do it delicatly, and carefully. you do not want to start solids earlier than baby is ready. sure signs are available www.askdrsears.com and mostly include interest, sitting up on own, able to tell you when they are done, etc.
any spitting out of food is a SURE sign of NOT being ready. if there is any spitting out, it is because they are not developmentally ready to bring the food to the back of their mouths to swallow. yes some food will get down, and you can eventually get baby to eat all of the food, but really, baby is not ready if they are spitting out. follow your instincts and baby's cues.
also, if its interest that seems to be a sure sign of readiness, make sure baby isnt curious about just the spoon itself. give her a soft spoon and let her be curious about it before giving solids..
most likely, at her age, this is a teething issue NOT a solids issue. yes, many babies can and do start solids between 4-6 months, but put it this way, the longer you can wait the better. the longer you wait, the more developed the digestive system gets, and the less likely there will be food allergies, sensitivities, or other digestive issues. baby needs to take it slowly.
my son started at 5 1/2 months old, he was developmentally ready, and he never spit out his food (of course, until he learned how fun it was for playing - thats different) he just took that first bite, and down it went! :D
so remember that.
its best not to follow the calendar with these sorts of things, but follow the baby and her readiness.