Does anyone else find that their co-sleeping baby won't sleep well without mum (or dad) there sleeping with them?

This seems to be the case with a toddler I know. I think she's tired the whole time, because she doesn't know how to get to sleep when she is alone. She's certainly really really hard to get to sleep, sleeps lightly at best, and is often a real handful (she's delightful in other ways too - it isn't all bad).

Her parents are doing the whole "attachment parenting" thing, which I haven't read much about, though I gather there is a lot of information out there about this. But it doesn't make sense to me to not teach your baby, as easily as possible, that it is OK, safe, and comfortable for them to sleep on their own. It also doesn't make sense to me to make someone who is upset about it have to sleep entirely on their own every time.

Surely there is a middle ground here?