This is kind of a tricky one honestly. If Sadie has joeys in pouch she will need the help of dad to raise them. But now you have another female that the male could of potentially bred with as well.
Putting the females back together I wouldn't advise at this point, one or both of them can get seriously injured or die if you don't know the fight is happening early enough.
Even if the initial introduction goes well, that is no guarantee the colony will work long term.
I introduced two pairs of gliders the intro was great, about 2 months later the colony still wasn't meshing. One of my females suffered some facial injuries from another female. We separated, aquired two more gliders for the singled one this trio worked very well. Later on I re introduced the two trios it worked for a little while, then one got a neck wound ( not from fighting) and had to be separated, then the same two girls started bickering at each other again. The colony of 6 wasn't working so we are back to two trio's in a different combination.
At this point, I would keep them separated, and get another cage for the single. IF the other female produces joeys perhaps one of the joeys can be the single girls cage mate once old enough to introduce.
The tricky part is, for the next 12 months both females can potentially produce joeys if the male is intact even if you have him neutered right now ( which I would advise doing ) Mating trio's CAN work, but it doesn't sound like that will be the case for you.
So now you have one single female who won't have any help raising the joeys if she does produce. If you do get her another cage mate ( male or female ) you run the risk of the new glider disposing of the joeys if there are any. It's a tough call to make and only you can make the decision.