My dd is four months, and this past week she is...

My dd is four months, and this past week she is stopping halfway through her bottle for a burp but then doesn't want any more - i have to get her to burp otherwise she throws it all back up (i went through 6 cot sheets in one day plus half of my shirts) when i try to put in her mouth she jams it shut and pushes it away with her hands but i know she is hungry cause she whinges about it half an hour later. could this be because she is developing an interest in us eating - she watches us like watching a game of tennis ie. follows the fork up to our mouth. so should i start her on rice cereal? and what can i do to stop her pushing her milk away?