I feel as if the movie is pretty clear that Ilsa respects and admires Laszlo. Certainly she loves him but in the passionate romantic way that she loves Rick.
Oh I think they are pretty clear about it. Even before Isla heads sees Rick for the second time it seems like that's the plan. As Ilsa Isla tells Laszlo that she is going to see Rick about the letters she says, “Victor, whatever I do, will you believe that I, that . . .”. His reply, “You don’t even have to say it. I’ll believe.” That seems to imply that if Isla plans to sleep with Rick and Laszlo indicates that he understands. Later Rick says to Laszlo, “She tried everything to get them, and nothing worked. She did her best to convince me that she was still in love with me, but that was all over long ago. For your sake, she pretended it wasn’t, and I let her pretend.” That's a tacit admission that the he slept with Ilsa. I always thought it was kind of a jerk move by Rick. I guess the best possible to spin is that Rick was trying to explain why he changed his mind on the letters of transit and he felt that a tryst was better explanation than confessing their deep and continuing love for each other.
This "psychic" (as they sometimes referred to it) moment by the Epsteins had less to do with the resolving the romantic triangle than ending the movie on a up note. Another ending had Rick being arrested. A noble, but unsatisfying end. The "suspects" ending redeems not only Rick but Renault as well and leaves the viewers to imagine there continuing adventure. It is a brilliant ending.
Like you I love this movie as well. It is outstanding from start to finish and stands up not only to time but to multiple rewatching.