[Steve428]

I found the answer to my own question. It is along the lines of what Denny was saying. Here it is:
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Section 135.115: Manipulation of controls.
No pilot in command may allow any person to manipulate the flight controls of an aircraft during flight conducted under this part, nor may any person manipulate the controls during such flight unless that person is—

(a) A pilot employed by the certificate holder and qualified in the aircraft; or

(b) An authorized safety representative of the Administrator who has the permission of the pilot in command, is qualified in the aircraft, and is checking flight operations.
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The question I still have is this:
---Question---
What if the student didn't take the controls, but still received multi-engine flight instruction; would this be legal and loggable time (Dual Recieved)? I think the answer is that only the required crew, PIC, and employees of the Part 135 operator are allowed to be onboard the aircraft, if the aircraft doesn't comply with passenger carrying requirments, which includes having placards about emergency exits, and also would require the PIC to give a briefing on smoking, emergency evacuation, etc....So, if my friend were to become an employee of the company, even if it meant she cleaned the aircraft, then she could legally be aboard the aircraft during flight, and also legally log Dual Instruction Received time if and only if she received instruction in the aircraft and she did not touch the controls.