I am curious, there is a little girl available in my area that I am very interested in picking up. I currently have a male and female couple that are about 2 years old, would I be able to add her to the group?

Any suggestions would be greatly appreciated.

Based on just genders i don't see why not. I added a lil lady to my male and female.

Not all sugar gliders get along no matter how hard a person tries to scent swap and to introduce them. That's the only problem I can think of that you might come across.