Ok i have a glider thats been with us for about two months now. My other two dont hurt her but......

They always kick her out of the pouch 75% of the time
They rarely clean her
Ther crab at her most if the time
They dont respond to her barking
They push her off to the side of the bonding bag and seperate her with blankets
They always pssst her
She plays alone in the cage alot
Shes the first to loose her food(no food agression she just gives it up)

Its like shes the annoying little sister they are always trying to get rid of. Ill repeat they dont hurt her.

There all aprox the same age withen a few months, same diet, same attention, same breeder.
Any insight would be great thank you.

How long has this been going on? Shes probably just at the bottom of the hierarchy, and she seems very submissive. Just keep an eye on their behavior, if there are fights and they do end up hurting her then you may have to separate. I've heard of gliders kicking one out of a group before, not sure if this is whats happening. Hopefully shes just the inferior glider of the bunch and they will treat her like this.

She's been with you for 2 months....how long ago did you introduce her to the other two? Are the other two female?

I would just continue to give them more time at this point as long as there is no obvious fighting. Do you have an extra pouch for them? If they keep kicking her out, if she has at least somewhere she can sleep, a hammock or something will at least make her more comfortable.
Make sure you have multiple food stations if you don't already so she is at least getting enough to eat. I had 2 gliders that did this for at least 2 months, if not more, no fighting, just one seemed terrified to go near the other for what seemed like the longest time. They are now completely inseparable, and it seemed to just happen overnight.

You have been given good advice. I'd follow it a bit longer, but if it continues,...me personally, I'd be looking for a 4th.

I say this because I have 5 in one cage. Started off with Jasper & Zoey at 8wks. so they've been together their "entire" lives. (aside from b4 they were weaned) I intro'ed Kodah and all was fine but about a week later I intro'ed Mala.... Kodah immediately took to Mala. While they all get along, no aggression or dominance issues they do seem to "pair up." When they get let loose in my bedroom for playtime, Jasper & Zoey stuck together pretty tightly but Kodah & Mala would as well.

When I intro'ed Ariana...the same thing. Jazz is a mamas' boy...if he can curl up in my shirt and camp out, he's happy - so Zoe being as hyper as she is, has a tendency to leave him in the dust...which is just fine with him, but Ariana is very similar to Zoey...I actually think she copies Zoeys behavior. I got her at 8wks. and the second I did intros she tried climbing on Zoeys back like she was her mama or sister. They are the first 2 up at night and they are the ones I can't open the cage door without both jumping right to me. So, now that they have been cage mates for several months, during play time Zoey & Ariana now pair up and play chase, hide & seek, & any other fun games they create. If I'm looking for Mala or Kodah, all I have to do is locate one of them and the other is not far away.

So I think if you got a 4th, you would probably see the same kind of thing... a pairing up of friendships.

Loki and Draya ( male and female ) are the ones who arent lovin her (Mesha). They are accepted her fine at first. This has been going on for about a month and a half. There is no food agression and she does get enough to eat, it doesent happen at the dishes lol. Just everyware else. There is lots of stuff to sleep in as well. I do watch them closely and so far no agression, just the above behaviours. I have also had to start carring Draya seperately as shes extreemly shy and gets upset with Mesha in the bonding bag. Drayas very different but thats another post lol.

Just thought someone knew why?

Personally I would still just continue to do what you are doing and just give them more time. The other two have obviously already formed a close bond, and it may be intimidating for her as a less dominate glider to try to integrate herself into that relationship. Animals are just like people, they all have different personalities. I would liken it to the same situation as a shy girl trying to work her way into any established group of friends, it will take her time to feel comfortable.