buddy, good friend, best friend, a friend of mine, my friend

1) She's my buddy
2) She's my good friend
3) She's my best friend


What are the differences among the above the sentences?


4) She's a friend of mine
5) She's my friend


What are the differences between the above sentences?

Thanks

1 She's a friend whose company is fun and I can do things with
2 She's a friend who can be relied on
3 She is the friend with whom I have the greatest rapport and who knows all my secrets

4 and 5 are essentially the same, though 4 is perhaps rather more assertive.