Is this really happening?

This past Tuesday-the 17th-they actually extubated Megan and within minutes her Co2 was too high and she was turning gray so they immediately reintubated. The doctor talked to us about our two options - a tracheostomy or extubating and letting her go. I have never cried so much as I have over the last 5 days. I came home to see the boys last night & as much as I miss them I really did not want to come home. I pulled up in the driveway and cried so hard because I am here without Megan. I cried on her bed in her room for the longest time while holding her little dress that she wore in my hand to smell her. Looking at her pictures in her room is too hard. I am so afraid and dont know how I would survive without her. I cant even explain how deeply my love and attachment for her goes. Her MRI showed decreased white matter in the brain and there is a space between her brain and the actual skull. The neuro says it is most likely atrophy/wasting which would be consistent with her disease and IF it is she PROBABLY only has weeks or months at this point. But nobody can tell me it definitely is or anything for certain. How do I know who she is yet when she still has a tube down her throat keeping her flat on her back and has gotten three infections in a row and is still on methadone wean and steroid weans. I am not ready for Megan to leave me and go to heaven. It probably sounds selfish of me, but I dont know that she is ready to leave or if she is just still so wacked out from meds and sickness. A normal child would need a long recovery and she takes longer than a normal child. I know this. My gut and my heart say to keep her here and see what she can do. If it truly is nearing the end for her then surely there will be nothing for her to gain, but I would always question what if??? Maybe I am being selfish but I cant help it. It hurts so much to think about not having her. I am in such a bad place with what has happened in a month. Werent we supposed to get the tube out in a day or two and then come home in a week? What happened to that? They also did an EEG overnight on Thursday until Friday morning. Thursday she was running 102-103 fevers and at 2:30 am she actually chewed a hole through her tube and had to get sedated so they could extubate and reintubate a new tube. The neurologist said that she saw "decreased activity" from the EEG a few weeks ago in the cortical region. I am not a dr., but isnt the point of sedatives to alter your mind? And activity level? Would that not affect the EEG. She says no, but I have had another neuro tell me yes. Also we have known for over a year Megans brain is not normal and she has less white matter to it. I was not expecting a normal MRI by any means but to hear that she MIGHT be having disease progression. How do I even look at the option of letting her go with the words, if, maybe, probably. Pat wants her to come home breathing on her own. That is impossible. The choices are to not bring her home at all (not really a choice for me right now) or get the trach and work on getting her weaned down from that. They are all not permanent. The doctors think it might be her brain not talking to her body to breathe - that the thermostat is breaking. Or she is too weak to breathe deeply enough - she has been laying down since about the middle of January now mostly and definitely for over a month now. She got pneumonia that caused respiratory failure - where did the brain thing pop in? Her breathing was fine until the pneumonia. I am so confused. Anyone who may read this who has any knowledge or experience in this area, please fill me in!!!!
Megan did smile and cry yesterday - both signs of a person being in there to me. Could have done w/out the crying, but I will take it - it is an emotion that she was feeling. I hate feeling so sad and helpless. Sad for Megan, sad for the boys, sad for Pat, sad for the grandparents and sad, sad, sad for me too. My heart really does hurt. When I cry I feel like hyperventilating and vomiting at the same time. A pastor told me that parents know when it is time to let go, they just know. Well I dont think it is time, because I dont know. I wish Megan understood how I felt about her. I know she used to, but I am doubting it now and it makes me cry to think about that too. I am her mommy!!!! It is so abnormal to question whether she knows who I am????? Have to get that tube out and get her out of that bed. Need to talk to Pat and get on the same page. He is sad, sad, sad too.