“woman allegedly sat down next to the officer and tried to start a conversation, an MPD source told WUSA9. The source said she then reached down and took a French fry from him as he was eating. The officer asked the woman to stop, but she took another.”
http://www.wusa9.com/news/local/dc/woman-arrested-for-stealing-french-fries-from-a-dc-cop/316128060
report says woman appeared to be drunk
She probably liked the cop and was making a move on him.