Leela hadn't known what to expect, but when the girl cried out for someone, a Simon, she was a little taken aback. Usually someone's response was either to answer the questions or attack, depending on whether they were friendly or hostile. This girl didn't fit into either of those, which meant she was probably as confused as Leela was. The warrior let her defenses drop, though that could be a problem. The girl did seem to a little distressed, something that Leela really had little patience for depending on the situation.
"There is no one by the name of Simon here, but my friend, the Doctor, may be able to help. The Doctor should be here somewhere." It was a matter of where exactly the Doctor was. The control room was a good guess, he did like fiddling around in there. But he could also be out in Lawrence somewhere exploring. He always did like poking his nose around new places, though Leela couldn't help but feel very uneasy about him being alone out there. He did have a tendency to get into trouble. Then again, so did she.
"I will not harm you, I am sorry if I frightened you. I was startled by your presence." Leela decided it would be best to take the diplomatic approach. Diplomacy was not her greatest asset, but something obvious was going on here. This girl had gotten in here somehow, found her way to this room, so they need to figure out why. "I am Leela." She assumed a non-threatening posture, her hands resting at her sides. She hoped that this would work because if it didn't, she'd have to go find the Doctor, and she didn't want to leave the girl alone. The TARDIS was large and the girl could get easily lost if left to her own devices.