Lily and Bella are lovely names imo but they just seem a bit too popular at the moment. Having said that, Lily can be short for Lillian, Lilith or, as PP has mentioned, Liliana or Lilybeth.
The same goes for Bella. There are loads of pretty names that you can use that end in "bella" so that you can use it as nn but your DD can have an option of having a more formal sounding name when she's older ifyswim.