Without being able to see your frame and wheel myself it is a bit of a guess. Still, 1 inch sounds doable with the right tools. (no guarantees, proceed at your own risk!) In the ideal situation you would try something like this: Frame spreader tool
to separate the rear dropouts and make enough room for your new rim. You have to be careful not to spread them too much however as you will damage the frame. You don't necessarily have to order a tool for this specific task. a length of ready-rod, a handful of nuts and a couple of washers would do the trick too. Then there is always the brute force approach as well. A scissor jack between the dropouts could work too. Just be careful.