Girlfriend lied to me, albeit about insignificant things, but still lied to me in the face when I asked her about something, and didn't confess until she knew I knew.

I have trouble trusting her about anything now, knowing she can lie to me with a straight face and I could never tell the difference. I took it as a sign of disrespect.

Could I in anyway make sure she won't do this again, or is there a chance I could read body language when she lies or should I just drop her and move on? I care for the girl, thats why I'm contemplating different paths of action instead of just the safest most logical thing here.