Was your daughter premature? As a pp asked, how old is she now.
The "condition" is called plagiocephaly and is very common in premature babies due to the amount of time they tend to spend in hospital lying down.
DS had it and when he was young it was quite noticeable; but over time (he's now 8) it has evened up and you would not in any way notice (obviously more noticeable for a boy with short hair than a girl with long).
All sorts of things are suggested on the net and by well meaning people such as helmets and the like but I would ask for a referral to a specialist centre (GOSH and Alder Hey where we were seen as DS also has craniosynostosis are two that I know of) and ask for their opinion.