The mode of calculation for canon law from the link in the previous question is reasonably clear.
The number of degrees is the number of people of the longer line of descent between you and your girlfriend back to but not including the first ancestor common between you.
You must be separated by at least 5 degrees.
You've been unbelievably unclear about your ancestry. Not a little unclear, astronomically unclear. Why are you complicating things by talking about your father's sister and your girlfriend's uncle? Is your aunt not a blood relative of your father? Is your girlfriend's uncle not a blood relative of one of her parents? What does it mean that your father and your girlfriend's uncle are not related? Do your father and his sister not share a parent? Please note my concluding statement, below.
Anyway, all you need to do is draw a chart of your family tree back to the first common ancestor and count the number of generations between you and that common ancestor (count every person in the line, including yourself and the common ancestor, and subtract 2). Do it for both you and your girlfriend. If both numbers are 5 or more, you're good to go. If either isn't, you're good friends.
Based only on what you've told us, you're separated by 2 or 3 degrees, max.
However, if your girlfriend's uncle is actually an uncle-in-law (someone married to your girlfriend's aunt), then the two of you may not be related by blood at all. You need an accurate family tree, and you haven't provided one.
Please note that an analysis of your specific family tree is off-topic for this site and will not be considered. The question of how Canon Law calculates degrees (assuming I'm right) has been answered.