Nursery refusal

Hi All

My daughter is 3.5 with speech delay and we are on the ASD pathway for diagnosis, primarily driven by her sensory issues with certain noises and delay.

She has been in full time nursery since she was 1 and whilst she has pretty much always cried at drop off, she has a great time there once she is settled, so its always felt more like shes upset to leave me rather than having to attend nursery.

Since Christmas she has started refusing to leave the house. I am talking apocalyptic levels of meltdown to the point she vomits. She has a solid routine, a visual timetable, positive time warnings. Its got so bad that my husband has had to start taking her in, because I physically cannot carry her while she fights. I have tried calming her down before trying again, but the same reaction happens each time. 

She has always been a pretty affable easy going child who is not prone to meltdown, especially prolonged ones so this new behaviour has come as a bit of a shock. She has started having a similar reaction to anything she doesnt want to do e.g go upstairs for a bath, but she quite quickly gets over it (a few minutes absolute tops).

Her behaviour always seems to peak in winter which I understand is quite common due to all the additional sensory overloads e.g more noise indoors but I just dont know how to both help her and its do distressing for us both, and I am worried about the knock on effect at my job.

Is there something I am missing that could be helping her?