I'm going to confront my girlfriend about her instagram DMs.
Why do you want to confront her about her Instagram?
I know she's talking to another guy, telling him private details about us
Talking to your girlfriend is a good idea, as the messages might be harmless and not as problematic as you think. That said, you should respect the privacy of your girlfriend and not read her private messages.
Sigh I have to confront her but I don't have the balls to do it.
If you feel that your girlfriend is disrespecting your relationship, you should talk to her about your concerns. This will help to improve the communication between the both of you.