Yes, Ivanova and Talia had a relationship.
Talia's actress, became a problem and wanted to be "The Star", so, this was her Swan Song, she is no longer on the show. If you remember back to the crazy episode where the Human VCR was recording Talia's reactions on a crystal for Kosh (When she examining the Kille's mind), and Kosh said "For Later" (or something close to that), the intention was to use that crystal to "fix" Talia, but, this is one of the very few plot points that got dropped in Babylon 5, since real world actress wanted to be "The Star" or to be released.
The Red Head, Lyta, indeed was featured in The Gathering
, but, The Studio wanted someone sexier, so, the part of Talia was written, and Lyta was removed from the canvas afer The Gathering