I didn't co-sleep, except for a little bit with DD3. It was really just a case of hauling her out of her carry cot into the bed for night feeds and falling asleep. Once I tried to turn over while she was still attached. Hoiked my nipple out and did turn and we all went back to sleep. But from twenty weeks to the day she slept twelve hours a night, unbroken, until she was about six years old.
But DD1 co-slept with GS1 until he was about two and a half or three. Nights were never noisy and she didn't seem to lack sleep. I think GS just didn't like being on his own, which is natural when you think about it, and he wasn't a deep sleeper. He's fine in his own bed now at three and a half and sleeps well.
It's just another option for a mum who needs her sleep, I feel. If he felt he wasn't going to be parted from her all the time, he'd probably grow out of needing her there, as GS did. She could also do this until she feels strong enough to tackle a tougher approach.
Just a thought. Good luck to her 