There's obviously more going on than just this possible break in for you to suspect she's lying to you. You just might not be able to put your finger on the exact aspects as to why you believe this. It's common. Most call it gut-feelings. Everybody gets those, but without going through some sort of communications courses focused on teaching body language, detailed verbal language, etc, it's really hard to communicate to others why you have that gut-feeling. Communicating with others from the same geographical locations are interpreted subconsciously. We all do it naturally as verbal and non-verbal communication typically falls into a normal range we learn from genetic predisposition (all humans feel the same emotions regardless of geography) and geographically specific social interactions.

Basically, if it doesn't feel right, it isn't. There is always more to it than you are getting from the overt communication. In this case, I don't think it matters if it's specifically a break in or not. There is obvious deception to one end or another.

Don't walk away, run.