explianing opinion on conversation

The scenario

Someone is across the aisle from yu on the commuter train carelessly talking on his cellphone. You overhear snippets of conversation suggesting an impending business transaction that might affect your friend’s company. She is already on pins and needles because of the state of the business her company is in. Do you relay the information to her, as sketchy as it may be?. I am looking for your course of action and why (or why not).