For a while, it wasn’t a problem and a 1 grid tall wall was working just fine to keep Mimzy out of my bird’s area. The reason I don’t want her over there is because of the mess he makes ie: seed, his pellet food, other food/treats, & droppings/ I have a small tray at the bottom of his cage that catches most of it. Which is lined with paper, that way I can just roll it up and toss it out when it’s dirty.
So lately Mimzy found out she can hop right over that 1 grid. I walked into my room and couldn’t find her! Found her on my bird’s area chewing up her vet reciept from her say >.< I guess that's what she thought of the visit 
So I now have the wall 2 grids tall but she is very determined!! Here’s a pic:
His cage is in the closet and as you can see, the grids are at an angle from her cage to the bird’s cage. The grids extend a little farther behind the wall so that there is no opening but she will stay there and shake the grids until she gets it open. His perch is right there too and I was trying to put it against the grids to keep her from getting over. (I’ve tried it on both sides of the grid wall) But she still gets it open.
I just put nails in the wall and bent them around one of the wires on the grid but I don’t think it’s going to hold. Any ideas on anything else I can do? My ideal for this would be to figure out some kind of tray that can hook onto his cage around the mid-section. That way, all of his droppings will land in the tray and Mimzy won’t be able to reach it. That way I won’t have to have the grid wall at all. Unfortunately, I can’t figure out a way to make the tray. He has a large flight cage. I don’t feel like the trays they make for bird cages are out far enough to catch all his stuff.
I hope this makes sense!!
Also, I guess they both like each other’s cages because I can’t seem to keep him off of her cage either >.< He flies onto her cage and hangs there right next to her while she eats. I tried hanging water bottles all over her cage since he's scared of them. He just finds another place to go -.-
Any ideas are greatly appreciated! Also, I’m unable to keep them in separate rooms, not possible at all 