A bonding bag inside a sleep pouch, if both pouches are made properly would be 4 layers of fleece, it gets mighty hot in two layers in the summer let alone 4 layers.
Air flow is important for gliders, if they are sleeping and over heat it doesn't take long to lose them from dehydration and most often don't wake up or alert the human there is a problem.
It would be safer to just remove the neck strap if you can from the bonding bag , leave the zipper open and put the whole bonding bag in the cage AS their sleep pouch not IN a sleep pouch. Even for just a week to get both their scents on it, which will help Nova understand it's a safe space for her.
However having said that, that doesn't resolve them not being easily transferred to another pouch and there will be times you will probably need to do so. So it's better if you figure out a way that works for you and the glider now and make it part of your routine or use the bonding bag as the sleep pouch for a few days then start to transfer them from the sleep pouch to the scented bonding bag...
I do it with new to me gliders by pushing the bottom of their sleep pouch up to the top then offer them the open bonding bag, close enough they can go right into the bonding bag from their sleep pouch. Most often even new gliders will dive into the bonding bag because the are more exposed in the sleep pouch. Since your other glider is used to you taking her in a bonding bag she will probably go into it first the other will follow her.
If you try it this way, set it as a routine, the same time every day, it won't take long for the new glider to figure out what your asking her to do in a non stressful way.
Putting a time frame on it is going to be the fastest way to be disappointed. Stop having expectations, especially time frames. It's going to take however long it takes, you deciding the glider should do X and Y within a certain amount of time is just unrealistic and unfair to the gliders, they don't operate like that, every glider has it's own time frame and it isn't set by the human.
Nova will warm up to you when she's ready, she's had a lot of changes in a months time and is still getting acclimated with all of it including her new cage mate and you.
Don't feel defeated, this is all a process for both the human and the glider, for as defeated as you feel, remember the glider is feeling stress and pressure and doesn't even know what you want from her for you to feel defeated that you haven't got.
Gliders sense emotions, and if your defeated that doesn't exactly instill much confidence for her to have IN YOU. Confidence is key, if your not confident, why should the glider be confident in you?