@Heather24, first of all, welcome.
As a parent, myself, I know dealing with behavior issues in any child can be difficult. So, when we add on the layers of difficulty with a child who is an "adult" and not living with you, I can only imagine the difficulties.
I know this is a deeply emotional situation, but forgive me if I am going to look at this from more of a logical or clinical perspective.
1. I think many autistics can relate to the fact that "meltdowns" don't just come from nothing. There is a buildup to this. Mental exhaustion and stress are often key triggers. What those are in your daughter, we wouldn't have a clue, but (1) a lack of sleep, (2) being overwhelmed socially, (3) being anxious for prolonged periods of time, (4) poor diet, particularly too much sugar, which is pro inflammatory in the brain, (5) physical pain such as from cramping from menstruation, (6) high mental demands, just to name a few. It is not uncommon to have these in combinations. You're at your wits end, and then, all it takes is something to "trigger" an event. As one might say,
"The straw that breaks the camel's back".
2. Misunderstandings are a common phenomenon. All we have are our own perspectives. We also have cognitive biases. It is difficult to relate to people, in general. I can try to fully understand what you are going through here, but I don't know you or your daughter or your personal relationship. Asking her to apologize for her behavior or what she may have said might not be something she would do, and I say this because in her mind she is correct. From her perception, such as it might be, often without all the pertinent facts, often without understanding how you are feeling, or how much it hurt you, she is correct. This has NOTHING to do with whether or not she was correct or whether or not you deserved that behavior or insults. You see the difficulties here? Neither of you know what you don't know. You are asking for help here, but she probably is, as well, but it just comes out violently in her.
I work in a large children's hospital. Our team of doctors, nurses, and therapists are dealing with horrible situations with stressed out parents on a daily basis. Some of our parents will be quiet, pleasant, and polite. However, we can only imagine the stress they are under. Some of our parents will be emotionally distraught and we need to console. Some of our parents want answers we cannot give them, either because we genuinely don't know, or its impossible. Some of our parents are just plain angry, and although they are angry at the situation, they will lash out at us. I may happen to be the face they see, but they are going to give it to me with "both barrels of the gun", per se. They are going to have their meltdown. I just have to take it, and definitely not escalate the situation my matching their energy or becoming defensive. This is a difficult skill and takes a lot of self discipline and control. I have to let them vent.
So, to answer your last question. I don't think you are going to receive and apology until you two can calmly talk about all the stressors in her life, as well as yours. If you do this right, it might be a beautiful mother-daughter moment. Let her talk, and for God's sake, do not interrupt. She may say some things that hurt you or are completely wrong, so your job is to take it all in, let her vent, and then when the time is right in the conversation, calmly respond with your perspective, your stress, but keep the energy low. You might find opportunities to help each other and find some solutions. It might be then that you both will realize what each of you didn't know, and your perspectives might change on the situation, and then, and only then will she apologize.
