yeh at this point I'd leave them together.
For meeeee, IF an intro goes really well I don't separate, from that point they stay together unless they start having issues after living together.
"seems like the little one is very attached/climbing all over/kissing/always right behind(possibly bc theyve each been alone for this time) to the older momma."
This is partly because they were alone for a bit and mostly because the 9 week old is still a baby and is using the older mom as her next best thing to her own mother and father.
Meaning the 9 week old is still in baby mode herself , riding on an older glider or larger gliders back is a young joey behavior that is normal even if the other glider isn't the parent or sibling.
The 9 week old will graduate and in turn be the one to give piggy back rides to the new joeys once they come out of pouch... acting as a babysitter helping mom get breaks to move without the joey attached to her.
Since the older glider is taking the piggy back rides in stride I would venture to guess they will do very well together and it's giving the mom to be some joey experience while giving the 9 week old some probably much needed motherly comfort as well.
I agree keeping them together at this point will reduce some stress for both of them and the 9 week old will glide right into being an awesome big sister to the new joey/s. But do monitor them if you see or hear any signs of issues don't hesitate to intervene