I wouldn’t really put them together until she’s spayed. You could start the pre bonding stuff like switching around litter boxes, stuffed bunny surrogates, etc…

Any progress you seem to make now in bonding has a good chance of being set back once she’s spayed.

I wouldn’t allow them to be together until she is also comfortable with her one leg and has learned to adjust with using three legs well. That way she can get away of need be easily.

But since they are interacting well through the bars I’d continue allowing that. But do not put them together until you see her comfortably and easily hopping around and until she gets spayed as when her hormones come to play it could all change or the bond may break when she comes back from a spay operation. But what you’re doing, allowing them to interact through the bars, is ok

Have you put her in an xpen yet or somewhere she can try and practice walking? Preferably a place with good traction like a carpet as fleece blankets on a hard surface can move when she is trying to hop and knock her balance a little off. I’m sure she will figure it out and adapt as necessary given time how long ago did she lose her leg?