I don't own a K5.. but there should be individual focus adjustments available in the menus ? Use a focusing chart to be sure. Theres a few threads around here.
Check if it persists in Live View as well - the K-5 apparently uses different focusing algorithms based on LV vs OVF..
The other tip is - I read on
Pentax K5 Photography by Jim Radcliffe site that apparently the K-5's AutoFocus Points are Larger than indicated in the OVF - this means they can pickup contrasting points other than what you think. He says a brief bit of experimentation solves the issue though and his 'used to it' now... maybe it picked up where the petals touch her face since it does provide some contrast to detect?
No idea though - just throwing suggestions out there I've seen reading K-5 threads...