acspears, if you take a photo of her belly we can tell you how far along she is. If the lump from the joey is peanut-sized and a foot is sticking out, the baby could be ready to come out in as little as a week as our2girlz says above.
However, if she is not far along, a foot sticking out could just be from the mom fluffing her pouch and it just happens to be sticking out. This is not always a good sign, by the way. First-time Moms with immature joeys who are teeny-weeny will often pull them out of the pouch and destroy them way before they are ready to come out - so a foot sticking out is NOT always a good sign. So hold her gently in your hand, roll her on her back, and take a few photos and post them here so we can take a look.
Regarding the spaying of females....
Females can in fact be spayed. I know two vets from separate facilities in this town who do it:
Dominic Cacioppo, DVM of Park Animal Hospital, and Christine Kolmstetter, DVM of Cheyenne West Animal Hospital. Dr. Kolmstetter is our USDA vet program doctor and our favorite in town.
Female spaying is sometimes necessary if the males (even after neutering) are aggressive in trying to mate with the females - especially if they are causing mating wounds. Mating wounds can be deadly and we deal with them here at the rescue year-round despite the fact that we neuter all incoming males.
Spaying is not a popular procedure as it is internal and invasive. Our practice at the rescue has been to separate females who are receiving mating wounds (two strikes and you're out) and pairing them with other single females. Now, that is a "luxury" we have owing to the fact that there are a lot of animals here.
But for glider owners who only have a male and a female, spaying the female is an option versus having them separated for life. Ostensibly, if the female is not going into estrous every 28 days, the male is less likely to be as aggressive in the mating ritual. So like I said, it is not a common procedure, but there are instances where it is actually advisable. Of course finding a vet who actually has experience doing it on sugar gliders and who knows what they are doing is essential.