Why do you go down just to be pissed off at her? Instead, don't bother in the future if all she is going to do is ignore you for the weekend. It works both ways in a relationship and you should not have to waste your time going down to see her, if all she is going to do is sit and do work.
I undestand that she may have a lot on her plate at the moment, but at the same time if you agreed to see one another, the last thing you should expect is to be sat on your own when you could be either enjoying your weekend yourself or doing something more productive.