Olivia twines her fingers through Peter's and squeezes a little - she appreciates the contact, a steadying reassurance that she's not going to flicker out of the universe again any moment... and that he's not a hallucination, like she was having before. She wouldn't admit it, but she needs that reassurance right now.

"Yeah. This is Steve Rogers. He's..." She should wait to give the full explanation until Walter and Astrid and probably Broyles get here. She has a feeling she's going to be repeating it a lot. "He's been helping me while I tried to get home. Steve, this is my colleague, Peter Bishop."

...colleague seems like a safe thing to call him, never mind that meeting in the lab, or that they're standing here holding hands. They haven't exactly had time to talk about... anything, figure out what they are. Olivia's just going to go with 'colleague' for now.