Sisters usually refer to female relatives who are related by blood, such as sisters or cousins. This relationship is based on kinship, so it has a deep emotional foundation.
Sisters may have experienced many things in the process of growing up, and they have the same memory and emotional connection. This relationship is usually long-term, but it may also be influenced by family factors.
A best friend refers to a very close friendship between two women, whether they are related by blood or not.
The best friend is the one who talks about everything, is the closest and knows each other best. This relationship is usually freely chosen, based on the same interests, values and emotional connections.
Girlfriend relationship is usually cultivated in a circle of friends and is not bound by family relationship.
Which kind of relationship is better depends on your personal situation and needs. If you and your sister have a deep family foundation, then sisterhood may be more important.
If you have a particularly close emotional connection with a friend who is not related by blood, then the relationship between girlfriends may be more meaningful.
Most importantly, intimate relationships based on respect, trust and understanding are precious to sisters and girlfriends.