Comments by the cast and creator
In interviews, the Babylon 5 creator Michael J. Straczynski and actors Claudia Christian and Andrea Thompson made it clear that there was always intended to be a romantic relationship between the two characters. Straczynski told Sci-Fi Universe (March 1996),
"We had it growing since the very first episode of the first season. The relationship was about all of that mutual antagonism that really means they're attracted."
Thompson also stated,
"There was a sexual relationship between Talia and Commander Ivanova. It was edited so that it was not blatant. But that was exactly what happened. It had been talked about from the very beginning" (The Creating of Babylon 5).
Christian suggested in several interviews that if Thompson hadn't decided to leave the show, the relationship would have been developed further, over a longer period of time. Because Thompson wished to leave, it was escalated relatively suddenly and brought to an end in Divided Loyalties.
"I think that if Andrea Thompson had not left, we would have definitely explored the relationship further. That was the intention, but because she wanted to get out, we had to wrap it up quickly" (SFX, July 1997).
Both actors spoke positively about the relationship. Thompson stated,
"Once I started thinking about it, the more I thought it could be really, really interesting if they actually explored it as though two women are in love, instead of doing it gratuitously... It doesn't bother me at all and I would happily do a love story. Those relationships certainly should be recognised, and it's ridiculous that we're still dickering around with the issue" (Starlog, Dec 1994).
Christian told The Official Babylon 5 Magazine (Dec 1997),
"I'll be quite honest, I was like the lesbian poster child; I got a lot of people writing to me from the armed forces and so forth, who loved the fact that they thought I was going to be gay. I'm not gay in real life, and I don't think I'm gay on the show, but I definitely think she had some kind of thing with Talia. I think a lot of gay women were hoping for that, and I didn't want to disappoint them; I thought it would be fun... Then Andrea left the show, so that's why it never came to fruition. The only reason it didn't go further is because we had to get rid of the character because Andrea wanted to leave. It could have been a long relationship."
It seems the also had a lot of fun filming their scenes together. Thompson said of their first scene in Signs and Portents,
"So they rolled the first take, and I walk out, and I say, 'I'm Talia Winters, licensed commercial psychopath!' Claudia just roared and broke into laughter. The whole crew did, and I had to join them because it was really kind of funny. That really broke the ice, and we went on to shoot the scene. I went on to be very close with Claudia. We spent many afternoons drinking champagne after that."
In the same book, Christian described the bar scene in the first episode,
"I think it was good in showing [Ivanova's] very tough facade slowly etched away by this person who has such insistence in talking to her. It was one of the nicer moments in Babylon 5, one of the most tender. And it was heavily laced with sexual overtones when we were shooting it because Andrea and I were just joking around so much".
Online sources:
First Lesbians in space.
Wikipedia.