I have a mini lop lol so yeah will be too big I thinkIt's too light, she could tip that over and the babies will end up all over the floor of the cage or wire depending on where you're housing her. Do you have a tractor supply near you? They have the metal ones for $20 although they're rather large, which may work for you-sorry I forgot at the moment what breed you have again. When I went it was wayy too big for my holland lop. I'm trying to think where else you could get some sort of wooden box.....
I have a wired fence I could drill holes and ziptie to the side of the cageLynzi how about one of those chicken nest boxes from tsc??... your right about it tipping, I forgot..I drilled mine to the cage floor which was wooden in that section, LOL those nest boxes are big, even for my flemish lol