I agree, with already given advice. I don't understand why you need to rush, but then I don't know your complete situation.
Can you keep two cages while you wait to follow quarantine protocol?
If the single glider is definitely stressed due to being a lone glider, which may or may not be the case, there are other factors involved such as a new home that could cause the stress, or parasites. Do you know the origin or any history on your girl friends glider?
If the lone glider is truly stressed from being a lone, quick intros could also increase the stress.
Here's my advice.
Answer the questions above, if you can know for certain the lone glider is stressed due to being alone:
1. Take to vet for check up and fecal. Take your gliders to vet for check up and fecal.
2. Bring glider into your home in their own cage for pre-intro procedure. While following the 30 day quarantine is ideal, if the stress is indeed due to being lonely and severe, quarantine can be skipped, just be prepared for possible future vet visits and treatment. Introductions however, CAN NOT be rushed! You must follow procedures, there are various steps with variables, but steps need to be done progressively. I recommend finding 2 people with experience to act as "mentors", that's how I did it.
If you are not certain the lone glider is indeed stressed due to being alone, please follow these steps:
1. Take the lone glider to the vet for check up and fecal.
2. Give the new lone glider time to adjust and acclimate. Stress could be due to new diet, new location, possibly both. There are definitely new scents for the glider to adjust to, and gliders are highly scent oriented and so much is determined by scent for them.
Please keep us updated on how they're doing and what your findings are. Wish you best of luck.