No-one's obligated to talk to a cop if you haven't done anything, (and walking on the wrong side of the road is hardly a crime. Hell, even I wouldn't stop. Might not run, but if I'm minding my own business he can go pound sand).
He was conducting an investigation into a unoccupied and/or suspicious vehicle (the truck right by her). He had no idea what the situation was and was simply trying to find out if it belonged to her. If I were a law enforcement officer in this situation, my first instinct would be to make contact with the woman because it appeared she was having car trouble. Her actions, based on training and experience based on the facts and circumstances of this rapidly evolving situation warranted further investigation. She had every right to remain silent during the officers investigation if she desired, but running from the police does not constitute exercising that right.
I don't know why everybody is so hung up on the whole "wrong side of the road" thing, he had plenty of RAS to make contact with the woman regarding the vehicle.