I'm going to get into an argument with my girlfriend about 6 month old texts
That feels unnecessary. Why bring up old texts just now?
So that I can argue with her regarding what she said.
I feel like it's just going to cause you more trouble with your relationships. If you have already confronted her about it in the past, there's no need for you to do it again as it can be seen as you holding a grudge and that is not healthy for a relationship.
I can just pretend that we haven't said something about those texts.
I'm thinking that if you are continually bringing old arguments then it is not a good relationship and your girlfriend may be suffering and she may not be telling you. If you really love her, then you shouldn't argue with her constantly, and if you don't love her, then I think it's time to let her go.