I love both
Olivia and
Anna. My two favourite girls names are
Olivia and
Annabelle :) I guess I like
Olivia a little more than
Anna. I would probably be inclined to save
Olivia for another daughter. But I'm not sure - when you say you love
Anna, do you mean as a first name for a second daughter or as a middle name for this daughter?
Isabel and
Olivia seem similar in style to me.
Anna seems a little different, more simple I guess, but just as lovely. For that reason I think
Isobel and
Olivia would be nice as first names for sisters.