OP are you getting a lot of disapproval from family? It is a bit of a "stripper's name" though there seem to be lots of little ones around so the associations will get much more positive.
If you love it and have your heart set on it, go for it, but give her a "sensible" name (Grace, Claire, something like that?) too so she'll have a choice and you can silence the haters! If you are a bit unsure you could always register Tallulah as her middle name but call her by it, then she's got her Sunday name for work, etc.
Good luck, people will come round in time (I know someone who picked something much less exotic but got LOADS of grief from PILs, she stuck to her guns and it's fine now).