In my experience, there's a process of acceptance and grieving that comes with letting go of any relationship.

You won't forget her, it's more like moving past and continuing on with your life.

Find a way to acknowledge that the relationship wasn't what you had hoped, and give yourself some time to process that- and whatever comes with it. It might be sadness or irritation, or a hundred other things. Feel them and acknowledge them as they come up. In time, what you had hoped would be, will be replaced with what actually was, and you probably won't miss her much anymore.