I have no real advice because everyone's babies are different and everyone has a different journey. However, I just wanted to let you know that you are not the only one and we know how you feel.
We had identical twin boys and also found we had severe twin to twin transfusion syndrome at 20 weeks and had lazer treatment. The smaller baby was measuring 3 weeks behind the other one with hardly any amniotic fluid and the bigger one had an enlarged heart so we were told without the lazer treatment we would lose them both probably within the week.
We managed to get to 27+4 before I went into labour and gave birth but we lost the smaller one when they were 18 days old. Our surviving son is now 9 1/2 weeks old, 37 weeks corrected, and it looks like he will still be in NICU for at least a month or so despite not having any major problems but I have been told that boys and twins do take longer. It is hard to predict how it's going to be but you still have every chance of your baby being OK even though you might not think so now. They will certainly do everything they can to help her.
We are in a room with two other boys, one born at 25 weeks, one at 24 weeks. They have had more problems than our son and needed surgery at times but they are now thinking about 'when' they will be going home not 'if'.