It seems to me that my girlfriend feels very much like an essay and in general is in love with herself completely. Tell me, do you have any experience in dating such girls as a couple?

And you think you understand girls so well? I think you are very wrong and do not have enough idea about what types of girls are and how to build relationships with them. For example, what about narcissistic girls? Do you know how to find an approach to them? If it's hard for you to do it, then I just recommend you this blog https://worldofarticle.com/narcissist-couples/ there are many useful tips about building relationships with narcissists and how to do it right. I think it will be useful for you to learn more