Wondering how to approach GP for referral when she masks well at school, so probably won;'t have any reports from them to go armed with.
I first initially noticed the PDA signs in her, but there are a lot of general Autism signs as well including sensory, the honesty, interupting, the focused and repetitive behaviors etc.
It breaks my heart sometimes when she is having a meltdown (once I have calmed myself down), because I can see how stuck she is for a way to manage what she is feeling. Have also been really upset when I saw her at a friends party freaking out about the balloons, afraid they may bang.
I would just be honest about your concerns. Talk with the school to see if they notice any issues. I would keep the line of communication with her teachers & GP to track behavior. If it is ASD the school should be able to notice especially if they know to keep an eye out. Wish you the best on getting her the help she needs.