This is an issue about communication.
Hardcore communication issues IMO too. It seems like you have a lot of pent up anger and you say you don't like arguments. It sounds like you keep stuff bottled up inside. That's bad, bad, bad.
If you can't be up front with your lady and tell exactly how you feel without it turning into an "argument" then you need to check temper.
If she is lying then there is a problem. Sit her down and find out why she felt she needed to lie and take it from there. You have to keep your head and be the one to tone it down if it keeps a little loud. The calm one controls the conversation.
Watch her body language. If it feels like she's being dishonest......
If you can't be honest with your lady and vice versa, it's never going to work.