OK, well...if they are not balling up and rolling around, I am honestly not that concerned.
My first pair of joeys was like this. They have NEVER gotten along *great*. In fact, I couldn't house them together at ALL until I finally gave up and brought another female into the mix to introduce to my girl Tanooki (because I was giving up on the other two, the male was just too aggressive), and then they decided they wanted to unite in their hatred of her. Long story short, while they are not the best of mates, they appreciate each other's company. But they often get into little squabbles...like pretty much every night...over food, treats, etc. Some gliders get along better than others.
like your two don't get along great. But if they are not balling up and damaging each other, it sounds
like they are not putting each other in danger. I guess you COULD always buy a second cage, and try to introduce a new mate to each girl, but there are no guarantees with that either. It sounds
like they are bickering more than fighting. When gliders FIGHT, they ball up, bite, and you can tell they REALLY, REALLY want to HURT each other. Keep an eye out that it doesn't turn into this, because then you would need to separate them immediately.
You really should have another cage handy since your girls are prone to fighting...I think Dancing's idea may be a good one. You can purchase a reptarium for pretty cheap...these are my travel cages...check it out...I have a large one of these that serves as a cage in a fix: http://reptiledepot.com/explorarium.html
As for touching Mimi...in what context have you tried to touch her?
My gliders don't really like being touched if I just stick my hand in their cage. But if they are sleepy in their bonding
pouch, I can pet them while they eat their treats, or if they perch on me at playtime at night, I can give them a little massage. I've noticed though that if you go "chasing them" with your hand to pet them, this usually just stresses them out.
Have you been working with her in the bonding
pouch, and at playtime at night? What have you tried so far?