amazingthingshappen.tv/
(I'm on stupid phone so link might not work. YouTube search for 'animated explanation of autism' if not)
Op, are you sure the girl is the issue? Sounds more like she is a symptom of how the school have explained this.
My son is 8 and has a diagnosis of autism with ADHD. He's had an IEP since yr1. We've been lucky to have good SEND teachers (and leadership). His classmates have generally been supportive and kind.
This year (yr4), his teacher talked to the whole class about him. I know she used a similar explanation to the one in the film link above. We watched this as a family, and found it really useful.
Children need to know things are fair. If this girl, or other kids don't understand why your son is getting 'special treatment', there's less reason for her to comply. She may have her difficulty regulating her own behaviour (asd the school rightly hasn't told you about), or she's been raised with anti social attitudes, whatever. Point is, how you talk to school should not focus on her, but your son, his needs and how the school are going to meet his needs. Fixing this one issue with this one girl doesn't address your concerns for the future about whether the school really understand your son's asd, and SEND generally.
My son's teacher linked how she wanted the kids to behave towards him to the school rules, and values. So as an example, she told them about why he has some extra needs (why he can't sit still), helped them understand how school met those needs (letting him wander when usual rule to be seated) and then put it in meaningful context for them (what rules still applied to my son, how everyone was different, and how this was another everyday instance of 'taking care of others'). In other words, normalised it iyswim.
Without that explanation in the round, perhaps other kids feel resentful of what they perceive as unfairness, be that queue placement, rewards, whatever.
As a parent of a child with asd, you know that information is your superpower. Don't be afraid to find, and share info like the film above with the school.