Ignore her, do not even look at her, to start with she will scream even louder but it gets boring when no one is paying any attention to you and your throat starts to hurt after a while I imagine

In public if the kids thru any kind of tantrum, I would pick them up, without looking at them, and take them out to the car, put them in their car seat, tell them we would finish the shopping when they had finished their tantrum and then shut the door on them.
I would stand where they could see me right beside their door, if they didn't stop within a few minutes I got in the car and went home (only had to do that once tho). It was easier if Des was with me bc one of us would take the child outside and the other would finish the shopping with the other kids.
Probably had to do that 2 or 3 times with each of the younger kids (Greg never threw tantrums in public thank goodness - it was a horrible shock when the little ones did it

) and they learnt it got them no where fast.
At home it was even easier, if they didn't stop after a minute or two I would pick them up, put them in their room and tell them they could come out when they had finished. I would then hold the door shut

yes it makes you feel like the worst mother in the world but after the first couple of times they give up fairly quickly.
Even at 8 or 9 all I had to say to bad behaviour was "Don't let us interrupt your tantrum, go to your room until you are finished" (which is what I always said to them when I put them in their room) and they would stop

they would pout and sulk but at least that is quiet right

In fact all I had to say was "Don't let us ...." and they would already be buttoning up

I did cut them a little more slack at home tho, as I told them, you behave well in public and you can let it out at home.
Sometimes they are just having a really bad day and need to just let it out. We have our friends to witch too, they only have us (Gee, aren't we the lucky ones

)