Children with adhd/asd

Hi all, I posted before about my 6 year old daughter. Currently awaiting assessments for adhd/asd. I wondered if anyone on here has a child with or going through assessments and how you deal with outside behaviour? At home its controlled things in place such as time out and I can calmly deal with meltdowns or "tantrums". I've been told by her teacher she tries her best to be like the other kids in her class but still struggles. My biggest issue is when in shops she has no understanding that it's not ok to just pick everything up no matter what I say. I have always had a bit of an issue but over the last year it has got worse, I got to a point where I would just not take her to a shop I knew was going to take a bit of time. Yesterday i was waiting to get cash out in my local shop she got bored of touching everything told me she was going to get this game i said no and she went behind the till and tried to do it herself. I obviously was extremely embarrassed and got her out from behind there, but needed to still get cash out. The staff was great but when we left the shop she demanded the stuff out of the bag and when I said no she tried to run off in a different direction straight out in the road! Then today she had come out of school in a terrible mood winding her brother up and ignoring everything I said. I had to go to Tesco we was in there for a second, as I was in the queue she ran off to the sweets and came back with some. I said " you are not getting any sweets because of your behaviour" ( I had already told her this before we went inside, this isn't a new rules either) she screamed yes I can! And a woman behind me made a judgy sound like I dont parent correctly and I wanted to just scream my self. I took her back to the sweet area and made her put them back she did it reluctantly but then refused to go to the car and shouted "I dont want a mummy". I got her in the car and just did not know what the hell to do, we had plans to go to a pottery painting place this afternoon so I cancelled that. She knows wrong from right and i am in no way a slack parent but sometimes I feel she does this in situations where she feels I dont have control? And advise would help me.