The Big Bang Theory Season 7 Episode 5
The Workplace Proximity
Amy takes a job at the same university as Sheldon. He doesn't have a problem with it, until Howard suggests it could be a problem. He tries to get her to turn down the offer, but it was too late. While talking to Amy, he reveals what Howard says about not wanting to work with Bernadette. Howard and Bernadette get into a fight and he goes to stay with Raj.
When Amy is at work, she says hi in the cafeteria, but eats with her colleagues. Sheldon stops by and embarrasses her. He doesn't understand why she's upset. When Leonard can't give him a ride home, he goes to Amy to get a ride. She's upset over his actions at lunch and refuses since she's not done working.
Sheldon apologizes though doesn't really know what he did. And, Bernadette tries to fix the situation with Howard, but he wants to stay and play with Raj instead. They are still fighting at the end.