Unless you are planning on having a child with no opinion - and I would say the odds of that are quite miniscule, I don't think you can count on her not ever being
Lily. Both
Lilian and
Lillian very naturally shorten to
Lily. If you adopt a different nickname early on, then it may be unlikely that she would choose
Lily, but she still may choose it and you'd have to get over it. Just sayin'
I prefer
Lillian, because
Liliana is a bit frilly and over the top for me. I agree that Lil is cute either way. An(n)a or
Liana could also work for
Liliana.