Picasso; noun. A girl who is a mess. Think of Picasso's work, and you're there. She has all the parts but they may be mis-shapen, unsightly, or even in the wrong place. This is not just limited to
girls with faces
like bulldogs chewing wasps, but it will give you a good idea of the starting point.
See also
Monet and Van Gogh
'That bird mings, what a Picasso'
or to an unsuspecting
victim, 'Scuse me Picasso, can I get past'
e.g. Jade Goody, Janet
Street Porter,
Sonia from Eastenders