It's on her border. Seriously, what other reason would someone need?
Note: the above comment should not be construed to imply that Solaria has it in for D'Hara. We in the Democratic People's Republic of Solaria love our wealthy grain clients to the west!
That was aimed at Indirik because him encouraging the idea so much seems like he isn't a fan of D'hara and he doesn't directly benefit since its not his realm that would be at war. That being Allison's justification I completely understand just don't know why Indirik would be against D'hara.