The sentence seems incomplete, it means:
'(My lady)friend sometime ....you....important you are for me'
(Missing: '....I'll tell/convince....how...' (?))
You are the best friend
You are not his friend on facebook.
It means "Since I met you, you are important."
you are my best friend and little sister.
It means, "You're still my [female] friend."
"I miss you very much, you are my best friend and I love you alot"
eres. 'you are' mala 'mean'
"Alguna" in Spanish means "some" or "any." It is used to refer to an unspecified or unknown quantity of something.
The first part, "eres muy bonita amiga" would be "you are very pretty, girlfriend." The second part "con esa mirada enamorada" would be "with that loving glance", but the third part "todo mundo preciosa" needs some work to be clear. Perhaps "todo el mundo está precioso", meaning "everyone is prescious" or "everyone is merry".
Tú eres = You are
what are you?
Amiga por vida means friend for life. (Amiga is feminine & Amigo is masculine)