To be fair, the 3rd person in these encounters just watched you cast a spell and, even if they couldn't recognize it instantly, probably saw the immediate change in the target's demeanor and can reasonably conclude you just used magic to influence/override someone else's will.
This is obviously not exactly what is happening going by your Zevlor example, otherwise he'd get mad *during* the dialogue. But if it is true that all parties get mad after the dialogue that you used friends on one of them, that's an acceptable compromise I suppose...
But also yes, always +1 for the game being better at explaining things and communicating what exactly is happening.
