Need advice asap!

hey!
My little girl Olivia is 18 months... she loved her food when she was been weaned and then started been fussy and not eating much. but now she wont eat ANY meals at all!! She will eat yogurts, and chocolate, but she wont eat crisps anymore either, but she cnt live off yogs??? DNo wot to do, ive tried taking her in n letting he rpick stuff and making things tgether but shes not interested, she just wnt eat.. any advice?
x