Hi there!
Sleep seems to be the hot topic among mothers and I can totally see why, it's hard! You would think that babies would just sleep when they are tired. I read somewhere that before 6 months of age, babies DO sleep when they are tired but around 6 months old, they start to be able to keep themselves up (like grown ups can).
I have the same issue with my daughter & we did the sleep training at night (which now works well, not to jinx myself!) but naps are a different story. Up until about a weeks ago, she would only take one nap a day & that was in the morning, in the Ergo baby carrier. So for an hour plus, I was walking around the house with a sleeping baby. It was freezing cold so I couldn't even go outside. One day I just had it & kept her up until she was really tired, then nursed her & put her in her crib. She cried for about 20 mins then fell asleep. Now she is quiet in her crib (not sure if she's sleeping) but it's a resting period none the less.
I read countless books and tried different methods but I think the truth is that nap time is so varied from child to child and it's all a matter of trial and error. I felt like my girl was tired of sleeping in her crib after she'd been there for 12 hours at night. Maybe your friend could try setting up another sleep nook for nap time, like a port-a-crib in the living room? Just a thought.
I wish I had a magic cure (the I would be a very, very rich woman!!)but every day and every baby is different. All I can say is your friend isn't alone and it is so hard sometimes. I read different books and took what I wanted from each one. You never going to know what works until you try it.
I wish your friend and all mothers with napless babies much luck and a world of sympathy.
C.