Many a maid of honor, informally

• Lifelong bud
• Closest buddy, to a texter
• With whom you might have a Snapchat streak, informally
• Closest pal, in texting shorthand
• Closest bud, briefly
• Chum, in modern shorthand
• Lifelong pal, 4 short
• Super-close pal, in slang: Abbr
• Maid of honor candidate

Wiktionary Word definitions in Wiktionary
n. (context text messaging Internet slang English) (initialism of best friend forever English)