Hi L.,
I am a mom of an almost 4 year old boy that didn't talk until he was over 3 years old. I expressed my concerns to his doctor who basically dismissed me and told me that boys talk later than girls and to not worry about it. It was extremely frustrating to me because he was not on track with other boys his age. I knew something else was going on, so I sought an evaluation by our local early intervention program. As it tuns out, my son was diagnosed with a speech and language disorder.
While this may not be the case with your friends son, I would encourage her to follow her instincts if she is concerned about it. She may be told the same thing by her doctor, but I have learned that doctor's are not always right. If she's not concerned about it, she could just take the wait-and-see approach.
If she is interested in an evaluation, she can contact her local early intervention program. The evaluation is free, and if they find he needs speech therapy, that would be free as well until he turns 3, and possibly beyond that. I don't know where you live, but in Sacramento you would contact ALTA Regional Services to get the ball rolling.
You're a good friend for being concerned for her.
A.