Soph, you're not doing anything wrong, on the contrary, you're letting your daughter go to sleep in the way she chooses to which is a kind and comforting option rather than traumatising her and yourself with controlled crying.
My SIL tried control crying and she had an awful time. Eventually she gave up on it and tried co-sleeping instead. Now she's better rested and far more relaxed and happy than in the CC days. having seen close up how traumatic CC can be for all involved I would think that the best thing you could do is to forget about it.
Yasin went from boob to bottle at 11 months and now he's 19 months he still has his bottle before bed while we read him his story. Its one of my favorite times of the day and when he decides that he's too big for his evening cuddles I'm really going to miss them.
We only have a 17 month gap between our babies and I think that having the comfort of a bit of quiet time alone with me or DH every night before bed has helped Yasin adjust to being a big brother. Although alot has changed around here bedtime has stayed the same and however fussy Imran is Yasin still has that bit of time every evening where he is alone with one of us for a bit of baby free/center of attention time.