I just checked myself there, their goal difference would stay the exact same, just get an extra point, meaning if we win our goal difference obviously will increase. If we win 1 0 and they draw 0 0, then all square with thistle and Spartans out, goes to goals scored, which again would keep us level with partick, then it goes to away goals scored which we have more of.
Or just win by 2 goals and hope they draw. And nothing else comes into it.