For you to be able say that she believes that she is hiding her actions from the audience you need to believe that is a plausible outcome. So, put yourself in her position - do you think, applying the straight face test, that if you were acting like her you could expect to escape notice?
I've not heard the other contestants say they have had no idea what is going on (whatever it is that is occurring). On the contrary I've heard just about all of them complain about Drew and Tully - because they see it as a weakness to attack.
And "just friends" is typical friends talk. What's your point?
I do not know of any attempts to find camera dead spots.
I repeat if there has been a breakup then Tully cannot possibly know about it. So, when she say she has a girlfriend she is not lying. However, as I've said, the whole scenario is part of a strategy. The evidence for this is Tully.