I think Emily is dying ... Please help me.

My female fancy mouse named Emily is approximately 8 months old. She lives in a 55g tank with 3 other females, and they seem to get along quite well.

This morning I woke up to find Emily dragging herself around the tank very slow and lethargic. I thought perhaps she had a broken limb, or something like that, so I thought I would try to pick her up and examine her. Here's the thing: Emily HATES being picked up and usually you won't ever be able to get her in your hands. However, this morning, Emily did not fight back. She allowed me to cup her in my hands.

I noticed all her limbs were fine and she had not broken anything. I looked into her eyes and they were HUGE and popping out ... I thought she had a little bit of blood by her eyes but I believe that was just me imagining and freaking out.

She was opening her mouth as if she was gasping for air, or wanted to bite me or squeak at me but could not do it. I thought she was choking, and I had no idea what to do ... I was getting pretty hysterical because I love my mice a lot and have yet to experience any problems health wise with mine ... I got my partner to hold her, and then had him put her back in the tank because she was twitching around and freaking out on my partner.

When she was back in the cage she continued to twitch around and at this point I had to leave the room because I myself was freaking out and I did not want to scare her ...

Shortly after being in the cage she began to breath normally, but just stayed in one spot and would not move. If she did move, it was slow and lethargic.

I got my mom to come to my place and watch her for the day while I went to work and make sure none of the other girls bothered her. The other girls stayed away but one seemed to be trying to groom her and make her comfy.

Emily eventually fell asleep in a curled up position in the same spot, and after sitting in that same spot for nearly 6 hours, she proceeded to groom herself, and then made her way back into her box house with all the other mice. They are currently all sleeping and I saw Emily move her head so I know she is still alive ...

Please tell me what you think is happening to my poor baby and how I can help her if at all possible? Do you think this is some kind of infection? Should I quarantine Emily? I just feel if it is her time to go, she should be comfy with her tank mates who she loves to be with so much ... however I do not want to wake up to my other mice having similar problems again ...

I have not changed anything about their diet or bedding and I know the rules - don't use any wood type beddings, give them a good diet, and clean their tank regularly without using any harsh substances ...

Thanks for everyone's support. Unfortunately, Emily passed away on our car ride to the animal hospital, one day after my post. They did an autopsy and discovered she had a tumor growing in her chest which may have spread to her brain causing seizures. It was very traumatic for both myself and my partner but we are coping well and buried her in a lovely forest near our home. We miss our spunky lil' girl. She was only approx. 9 months old ... really sad.