If she just hit 90K or 180K the light is suppose to come on as a reminder to change the O2 sensor. There is a reset button behind the dash (you have to remove the dash)
http://www.automotiveforums.com/vbulletin/t167700.html
http://forums.vmag.com/pthombre/messages/228.html
here is a real good how to with photos:
http://www.houlster.com/amigo/how-to.htm#O2_light