This is a multi-step badge. In the first mission of the Dr. Aeon Strike Force, talk to Becky the Tarantula Mistress at the receptionist's counter. Take her hostage, and bring her with you to the end of the mission (she's invincible). Make sure you bring her to the final objective, which appears in the upper level after you defeat and interrogate the Head of R&D. If done correctly, you'll receive a clue. She will then appear in the final mission of the SF as Battle-Becky, the Tarantula Mistress. Here, she is not invincible, so you will have to keep her alive as you fight through. Once you've defeated the final boss, bring her to the final objective glowie before anyone clicks on it. Doing all of this correctly will earn the Best Friends Forever badge.