I'm not an expert, but I would say that looks like self mutilation. There isn't a whole lot that can be done as she did just lose her mate. A few things that might help is spending more time with her. Do lots of tent and out of cage time with her. Also, try a few different foraging toys to keep her distracted. Also, I'm not sure how true this is, but I have heard that sometimes gliders might do better on their own for a but. I wouldn't really trust this, but maybe smeared them one night and see if the baby is bullying or annoying the mom. If she is, maybe you could give separate the mom for a short bit. Also, it never hurts to talk to a vet one more time For some extra advice.
Hope this was able to help:)
Like I said I'm not an expert but thought I would share this incase it might be help:)