Two cats brought together at a young age get along. Adult cats have a harder time, though some do warm to eachother eventually. What I've got here is one of the more difficult situations, one adult cat that's lived alone a long time and has established this whole apartment as her teritory, and one new adult that's also lived alone and isn't used to sharing!

I'm sure they'll at least get along, I don't anticipate any real fighting. But they have had one confrontation, with lots of hissing and posturing and showing of claws.