WINONA, Minn. —  A woman who claimed she had spent New Years Eve as a sober driver to transport inebriated friends home safely was herself arrested. The charge: Drunken driving. It was about 12:40 a.m. that a police officer spotted Sara Marie Walchak, 28, of Winona, in a car stopped in the middle of Olmstead Street between Fourth and Fifth streets. She climbed out and walked around the vehicle looking confused, the officer said. Asked what she was doing, she answered she couldn’t get her headlamps to work. The officer found the switch and turned them on — and smelled alcohol.  Walchak claimed not to have been drinking, but the officer observed bloodshot and watery eyes and conducted field sobriety exercises. A breath test suggested intoxication at 0.10%. Walchak then remembered a tequila a half hour earlier, the officer said.  Later at the jailhouse she tested at the 0.08% threshold for impairment. It was the city’s first DWI case of the new year.