She has to be right

Im 20 and my girlfriend (also 20) cant seem to ever be completely wrong..... Everything she says has to be a little bit right.... to the point that I have to get someone else to prove otherwise she will shout and scream that she is right. I have gotten to the point that I lie an excessive amount because of it..... I lie and say that I dont know or I dont remember. But from time to time that even makes her annoyed with me. Im even at the point of saying sorry but not knowing what Im saying sorry for. How do I confront her about it? or what should I do?

I've a friend who has had anger issues in the past, if I dared do anything to question her she would blow everything out of proportion and I'd be the bad guy. I used to apologise and try explain my point and it was the WRONG response. It just encouraged her to get more huffy, also it made me out to look worse in her eyes as my apologising to keep the peace just reinforced her belief that what she was saying to me was right. Rather than going out of my way to prove I wasn't in the wrong, or try explain myself, which just made things worse and turned a tiny disagreement into a full blown tirade in which I was made out a heartless villain, who was selfish. I basically stopped taking the bait and started giving her a single, curt but courteous reply..thus stopping her need to reply in anger or to validate herself/invalidate me. It made all the difference, she started apologising when I done that and now she's stopped pulling that nonesense at all (well so far lol).

Do you want to marry her? I think she is a very difficult woman in other ways too and you should think hard about looking elsewhere unless you want to put up with this forever. I don't think she can be fixed only modified and it is up to you if you want to do this.