Very close pal, informally

• Closest pal, these days
• Soul sister, slangily
• #1 texting pal
• Really good buddy, in textspeak
• Chum 4 life
• Closest buddy, to a texter
• Fave in your contacts list
• Permanent pal, in textspeak
• Teen girl's close chum, for short

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