Some posters are writing with an incredible degree of confidence that their approach is the one and only way forward. It may have been the right approach for their DC, it may even be the right way for the OP's DD. I have no way of knowing and neither do they! A 'hardball' approach that assumes the behaviour is no more than 'attention seeking', may not just be unsuccessful, it could be damaging. Again, I'm not saying it would be in OP's situation but to ignore the possibility is unhelpful.
It is possible that OP's DD is only just 'coping' at school. Whether or not she an ASD, it sounds like she finds things more challenging than most of her peers.
She may have exhausted her emotional 'energy' just getting through the day. And when she gets home she may actually need this unusually high level of reassurrance to wind down and recharge for the next day.
It is possible that OP's DD may have some undiagnosed additional needs. If that were so, then if these were identified it might focus support at school.
It frustrates me so much that people assume that if the 'behaviour' is observed at home then the solution must lie at home. This is NOT necessarily the case. Children (particularly girls with ASD) often mask their difficulties at school and display the signs of not coping when they are safe at home.
I disagree that assessment / diagnosis would not be helpful. Those posters seem to think it would be unhelpful because they regard the only solution is the behaviour modification approach so confidently advocated above.
It is possible that the solution lies at school or elsewhere, we simply do not know.
OP, I personally would involve school and GP and push for CAMHS referral and consider other referrals - I'm not diagnosing but raising possibilities e.g. dyslexia, sensory processing as well as possibly ASD.
If your DD needs your attention, and you suddenly withdraw that attention and ignore any signs of distress resulting from that, it is possible that this could cause more problems.
As I say, I don't have a crystal ball - but neither do any other posters. I just want you to consider all possibilities.
Good luck