I don't know you, obviously, but I think you and Tim should both approach her together. If you are at all interested in trying things out with her again, I would strongly suggest it. We refused to "go unicorn hunting" and it took six years for a nice cute girl to find us totally by chance, and I consider us all three very lucky, even though not everything's perfect.
In mainstream monogamous relationship world, it might be true that "there are other fishes in the sea." But for a poly couple looking for a bisexual woman, there might be like two other fishes and they're hanging out in some cave in the Caspian Sea. Stupid metaphor, I know, but I really think you should give it a shot with Clara unless you are too devastated by the past breakup and can't survive living through it again.