Bribesmaid

A bridesmaid who, upon learning that she's in the running for the position of Maid of Honour, begins to schmooze to tip the odds in her favour. This could include flattery, doing favours, buying gifts and other general ass-kissing.

Alvin: "What's with Mary? She never has time for me anymore"
Toni: "That's because she's too busy being Kate's bribesmaid"
Alvin: "Oh man, not again"