I don't think you'll have a problem with
Alice. I think it's short enough that a nickname wouldn't be automatic.
Julia on the other hand...
Julie or
Jules might be unavoidable.
I don't like Phi or Phina, but people have been suggesting Sephy and Raphy, which aren't bad. I'd never use
Nico on a girl, as I would never use any name that ended in 'o' on a girl.