After finishing Paparazzo - The Partnership, there will be two green circles that appear on the map. This one is located in Downtown Vinewood, so head there and you'll get a call from Beverly. You will want a pretty fast vehicle for this mission. It appears that Poppy Mitchell is being chased by the cops and is drunk, with Beverly wanting you to follow the actiion.
Keep following the cops, looking out for other vehicles, as crashing will put you way behind them and possibly make you fail. She will eventually pull over and you will automatically stop. Get out of the vehicle you're in and bring out your phone. You want to snap a picture of her, so make sure you get a clear one. Send it to Beverly when you get a good one, then leave the area to finish the mission.
