OP- I think you are right NOT to force her to do anything she's uncomfortable with. I know personally how Hard it is to have a child that *should* be able to be away from you for a while, but they cannot

I applaud you for listening to your gut and your child. I'm so sad that she's acted out at daycare as well...how difficult for all involved.
I have a DS that's very anxious. He's probably SPD and he definately has some Autistic Like behaviors- but isn't autistic. He does have moderate anxiety. His anxiety varies from age/stage to situation to location to scent in the wind...lol well it seems that way some days. We have tried lots of ways to combat my DS's Anxiety (not therapy, I'm not a fan of therapy in children unless it's ABSOLUTLY nessicary) and the only thing that seemed to work were these ideas. 1-Calm Child herbal pills. They work very well and instead of treating each "melt down" he had a base of calming medication in his system. Very highly reccomended! 2-lots and lots of talking about what his brain was doing. That yes, it sucks but it is something he can work to controll. We also worked on ways of getting him to calm himself in the Moment (and carry an herbal liquid called tummy tonic- for whatever reason it helps tremendiously during an attack) and ways for him to tell us he's Overwhelmed or stressed before it's bad. 3- making sure he knows that we love him, and that if he's scared or panicking we will not force him to do/go where he's uncomforatble. He had a total panic attack over leaving for the store. Out of the blue. I stayed home with him and he sat on the couch and cried next to me. He didn't want to talk, or touch me or watch tv or anything. We just sat there and cried, and when he was done- then we talked about what he was feeling and going through. He told me what helped him, what made things worse at that moment and we looked for ways to improve the next situation if there is one. Sometimes he just needs a firm voice to tell him that he's going to be OK, and that he needs to keep breathing and to stay with him.
I think you are doing a great job. It's very difficult with kids that panic, so hang in there and trust your gut!