Not as easy as some may think getting any 2 chins together.
Some are mates/friends from first meeting, some can take some coaxing, and some never will get along.
I love the "time out cage",
and have used it many times. Just never called it that, good one Abby
I have some small cages made with very small mesh, and have put the bullies in it while their hopeful cage mate runs around them.Works great for first meetings too as no one can get bit, but they still get a face to face meeting.
There is a more smushed method, using a carrier, box or tube just big enough for the two.They don't have room for attacks, but plenty close enough for scents.
You can add a shake of powder to the dust bath to help them both smell the same.
I don't recommend this on a regular basis, but for introductions it won't hurt. Go for the cheap corn starch based powder, some are oiled base.I just don't think they be very good on their skin, as dust bathing is needed to dry up the natural oils.
Switching them to each others cages may help.
I'm not sure I've ever seen jealousy in any of my chins, and wonder if somthing else may have peed her off.
I've seen a scattered one pout if I don't do or give them what they want. But more like if I move their cage and they don't like it they seem to stress out a bit. Or move something in the cage, but never over seeing another being better treated.
I have many that love to throw things around, and have most dishes bolted onto their cages.
Your doing a great job but I'm getting the feeling this is going to be a bit of a tuffy.
Most of all you'll need patients, and time.
Remember it's quite possible these 2 will never be able to be housed together, and it will have nothing to do with what you did or didn't do.Some just don't like each other.
If there is a bully and a mellow chin, you may find it just too hard on the mellow chin and have to give up.
Watching for more hopeful signs