All those are tell-tale signs, but it's really a non-issue. If you're with a woman that is constantly showing low interest and disrespect, it shouldn't ever matter whether or not she's physically unfaithful.
There is a undue significance placed on cheating as a dealbreaker. Most men will agree that cheating justifies ending a relationship--what about all the stuff that leads up to the act of cheating?
Men that cheat will do it regardless of how happy they are in their current relationship. Women aren't like that--unless you've got a psycho (which is possible, don't get me wrong), her cheating is really just branch-swinging prematurely. In other words, she's already made up her mind that she doesn't want to be with you. A woman that truly values a relationship will not jeopardize its future by cheating.
If everything in your relationship is fine and dandy, you have no reason to watch for signs of infidelity. If things are bad, infidelity on her part is certainly possible, but it is STILL a waste of energy trying to catch her in the act. If you're to blame for her low interest, try to address the problem by acting less AFC. If she's to blame, dump her. Scrutinizing her behavior for signs of cheating is counterproductive to the goal of raising her interest level at best, and a pathetic way of clinging to a dead relationship because she "technically hasn't done anything wrong" at worst.
You can't really trust your gut to tell you that she's cheating, but you can trust your gut to tell you when something's amiss in your relationship. That's all you need to know, IMO.
Given the hypothetical choice, I would rather have a cheating girlfriend that nonetheless treated me like a king and showed me all the love and affection in the world than a disrespectful, disinterested, resentful yet faithful one. This choice will always remain hypothetical, however, because the first option doesn't exist.
