Hi,
completley normal behavoiur at this age, my Dd went throught he exact same phase and luckily it didn't last long
At this age they start to get independant and want to do everything themselves, if she is keen to feed herself i would perhaps give her finger foods that she can pick up and eat easily and progress from there. i also put a plastic food mat under my dd highchair to catch all that messy food she dropped
i know when our 'super eaters' all of a sudden seem to be eating less we tend to panic that they are not eating enough but infact toddlers eat the amount that they want to and you would be surprsied on how many calories they can survive on.
like i said it is a phase they go through and soon she will be eating you out of house and home again
HTH
xxx