Plugin Enabled only for certain themes…

Hey, I have different themes on my blog. I recently downloaded the hemingwayEx theme and installed it. It’s great. But it has a pagination issue. So to fix it, a plugin was developed by some random person. It does the pagination well when the plugin is active. The hemingway theme is configured to show only two posts per page. It looks pretty neat like that. So the other themes which show ten posts per page get affected also when the plugin is active. So I was wondering if there would be some way by which I could setup a php if on that plugin so that it only activates itself only when the hemingwayEx theme calls it…
Please help… Any help is appreciated
Thanks in advance…