IIRC, Leila joins you very briefly for a very unimportant event post-Ultima Tome. I will go get the guide book and edit this post after finding the results

*leaves and expecting edit*

*forgets to click sumbit, post does not go through yet*

Indeed. Whenyou need to go to the "mirrior on the wall" so you can enter the cyclone (via Wyvern), during that brief event of going downstairs, Leila will be in your party. This is post-Ultima Event