You're not doing anything wrong techno, babies just have different sleep patterns. She won't do it forever - not that that is much consolation right now!
Are you offering both breasts at each night feed? (I only ask because I generally haven't unless DS has particularly indicated he's not done, but someone told me that seemed to help their baby sleep for longer)
You are probably just experiencing the tail end of the 3 month growth spurt, and fingers crossed she will change her pattern soon. DS all of a sudden went from waking every 2 hours to doing 4 hours at the first stretch after bedtime, and increasing up to 6 hours (until the next growth spurt came along!).
Just before he started sleeping for longer, I was thinking "I can't take this any more, maybe I should try some formula to see if it helps" (as all my friends' ff babies were sleeping FOREVER at night). Then when he slept for longer a few nights later, I realised I didn't need to. And I am not at all smug that the aforementioned 12-hours-a-night ff babies are now waking up several times a night as they hit the 4 month sleep regression, no not at all... (actually, I'm not smug, as DS' sleeping is so utterly random - but I hope it made them regret all the bragging they did earlier on!!!)
We had a long walk along the river today so I'm hoping all that fresh air will help DS sleep well tonight 