It's entirely possible that she was worried about prostitution charges. Who knows what was said as the "ladies of the evening" left that house at 610 Buchanan? Maybe the guys told them they were just a couple of skanky hookers, and they figured they would come with a story to pre-empt them. Just a thought.
Clearly Mangum and Pittman [aka Roberts] had good reason to contact an attorney after that night. Roberts was in fact arrested. In addition each may have thought they had a civil cause of action, but my guess is that both were more worried about criminal liability.
If I was a betting woman, which I'm not, I'd wager it was the lineup, make that six lineups. Was she feeling pressure to ID the "perps?"
Just another thought. :)