Oh, chicky There's nothing as demoralising as comparisons! And you know, 'sleeping through' is defined by different people in creative ways - it could mean that the baby wakes but doesn't wake mummy up cos she goes back to sleep by herself...so, not true 'sleeping through'. In fact, most adults I know don't truly 'sleep through, either!
If she's done CC, then that could explain her theory that the baby has 'slept through'. If baby knows no-one's coming to him, he learns that energy is wasted calling for someone who's not coming...and will eventually go back to sleep without calling for anyone.
Other babies do just go to sleep, wake quietly and resettle...these babies are far and few between, though, so there's no need to beat yourself up if yours doesn't do this!
We co-sleep and sometimes it's just easier, when someone asks, to just say 'yes, he sleeps through', but I do feel like a fraud when I do this...it's just sometimes easier than explaining that he stirs, latches on, drops off again, maybe once, maybe 4 times in a night depending on the kind of day he's had, or if he's been sick etc. I do feel like I'm doing a disservice when I call this 'sleeping through', because people assume that we don't have to tend to him even though he's not actually waking up out of his sleep whilst we do it.
No, my DS at 2 may not starve if I don't BF him overnight, but it's what he wants, he likes it and by co-sleeping, it means that even though I come out of a deeper sleep I'm not actually that awake, either!
The times I do have to fully wake up for him and he's more awake during the night are when he is unwell...and no matter whether you co-sleep or your baby sleeps in a shed at the back of the garden with a monitor (just being cheeky to make my point ) if your baby is sick, ain't no-one gonna get a great night's sleep!
YOU are not doing anything 'wrong' except using someone else as a yardstick, ok? And please dont' be lonely - if you haven't already, join a playgroup, a library kids' reading time, local ABA group...no mummy should ever be alone