One joining in on a ladies' night out

• Rhyming friend
• Tabloid's gossipy identifier, maybe
• Sidekick at a chick flick
• Girlfriend, in tabloid headlines
• Bachelorette party attendee
• Certain close one
• Ladies' night attendee
• Female friend, tabloid-style

Wiktionary Word definitions in Wiktionary
n. (context slang English) A female friend or girlfriend.