We used it against the BM between lawyers and the law guardian saw the copies we printed out... not in the trial. It just showed the type of person she is. Focus on what is going on. You can ask BF if he ever smokes on the stand. If he says no, you can use the picture and ask if that is him smoking... BUT you have to prove that he is smoking around the kids. If he lives with the mother, you can ask for a drug test of all parties (you too) and that will show it.
He said, she said is normal. Put all negotiations in writing (email or registered letter) after the phone call to review what was said. Do not worry too much what her family thinks... They will be supporting her (usually) so focus on the goals.
Good luck! (bring everything you have to court, you never know what will be brought up)