Good luck proving impairment from Pot. She may have been impaired or not but the evidence isn't clearly stated in the article. This could well be a case of a bicyclist failing to yield at driveway.  Cops evidence regarding impairment is always suspect, too. They are taught from scientifically falsifiable materials and many of them have demonstrable bias. The scientific evidence that pot impairs driving is weak, too. http://norml.org/library/item/marijuana-and-driving-a-review-of-the-scientific-evidence .