Yes, you're right. It's natural for humans to be attracted to other humans, but not necessarily in a sexual way.
Where women are concerned, I think that being attracted to other women is evolutionary. Women would have had to stick together in order to take care of children, cook, make clothing, etc, while the men hunted.
It might be both a combination of appearance and personality as certain indicators in each would have meant that that particular woman had a specific set of traits necessary for survival. For example, height, strength, intelligence and more would have been crucial for survival.
These days, some of these tendencies to look for individuals with certain traits obviously don't mean that we're looking for others to help us survive, but I think it's more about surrounding ourselves with people that can support us or people who simply make us happy.
Hope this helps!